I've failed 114 times now over the course of 8 hours, and so, in somewhat of a fit, but more-so in an act of desperation, I've decided to come here seeking help from my fellow warlocks on completing this quest. I know some of you may be thinking "Aren't there already enough threads guiding players through defeating this boss?" and while that may be true, there aren't any that detail how to beat him as Demonology, or particularly in PvP gear.
I'm going to start off by saying I completely despise Destruction. I dislike it's playstyle, and I'd much rather not be forced to use this specialization for the encounter. In addition to that, after my 29 hours of farming Isle of Thunder for the book, and reading through a few guides, I immediately stocked up on Drums of Forgotten Kings, Purification Potion, Flask of Warm Sun, Mogu Fish Stew, Tome of Clear Minds, and Potions of Jade Serpent.
After spending slightly over 2k on these preliminary items, I set off to complete the quest, and to eventually, defeat Kanrethad. My stats when buffed are roughly 417k Health, 20900 SP, 4% Haste, 12% Crit, 16% Mastery (And 54% PvP power, 66% Resil.)
After giving it a few test attempts, I realized that my glyph and talent choice wasn't suitable so I switched over to Soul Leech, Shadowfury, Unbound Will, and GrimSac. (That is, after trying out Harvest Life, Dark Regen, Mortal Coil, Howl, Blood Horror, and Archimonde)
I switched my glyphs over to Siphon Life, Enslave Demon, and Shadowbolt. (Which, after a bit of testing, and perhaps blinded by the aesthetic, I felt it did more damage than the regular Shadowbolt.)
Now, skipping ahead to the fight...
Using the narrowest area between pillars (on the left when looking at his soulwell from the stairs), I set up my Demonic Portal halfway inside, as well as my Gateway, which extends from halfway inside to about 120 degrees on the ring around the room, extending the shortest distance possible, and used both to escape into the crevice when he's casting, and reduce aggro. I've also tried using both pillars to the south of him, and wider areas between pillars near his gate, but it is with this setup that I've found the best results.
The reason I need to use both my Demonic Portal and Gateway to escape are simple. I can't survive a Chaos Bolt unless I have every cooldown up, which isn't readily available because I'll need to use it for the hounds. I also use this setup to avoid nearly 75% of his DoTs.
I start off the fight using my Imp Swarm to generate Demonic Fury, while casting long-lasting effects like Corruption, CoE, and Doom. I cast off two Gul'dans followed by two Molten Soulfires. From then, I pop badge, dark soul, and go Meta. I use Touch of Chaos until Chaos Wave comes off cooldown, which is conveniently at the end of his first summon and my Demonic Fury. His health rests at 97%.
I quickly stun and tame the pitlord, which I pit against the boss using his auto-cleave and his breath macro'd to my Hand of Guldan, while also using it on my own occasionally. (I have it macro'd to HoG for whenever the Imps show up.) I use my Demonic Gateway as often as possible, forcing the boss to fight my Pit Lord instead of myself. During this time, I cast off multiple Shadow Bolts, Soulfires, and a few Fel Flames. I immediately singe the first magical debuff he puts on me, while teleporting the second. If he uses Cataclysm, I charge, as expected.
By the time he summons the imps, my mana is around 45%. I use Sacrificial Pact and two Life Taps, followed by the Pit Lord's 210k heal to restore myself and protect from the imps, knowing Sac Pact will be up again in time for the felhunters. In the scenario that the boss got DoTs off on me while I was preparing, I will occasionally use Unbound Will at this time also. I immediately shadowfury the imps, while stacking two Gul'dans, and sending my pit lord over to breathe on them. There are a few problems I've noticed at this point, but none of them are game-breaking. Due to Hand of Guldan's buggy LoS, I can't walk/teleport behind the pillar or the meteor simply won't hit the target or do any damage. On the other hand, the pit lord's breath has a habit of missing targets that are directly underneath of his mouth, and is typically incapable of hitting all of them at once.
With a bit of persistence though, and a repeat of that process, I kill all of the imps without losing much or any health. I continually cleanse and teleport his DoTs, and again, restore myself the same way as earlier. Chaos bolts and soulfires aren't really a problem due to the amount of time I use Demonic Gateway to reduce my threat to my pit lord, and even a superstitious soulshatter here and there.
While he summons the felhunters, I use Imp Swarm, giving the imps time to get over their delay before they start casting. I use my pit lord's stun as soon as possible, stunning the first one who comes out. I then pop my cooldowns while spamming Touch of Chaos. It typically falls within 5 seconds. For the next two, I use two Chaos Waves to slow them while spamming ToC. There is a lot of difficulty for me at this time. My damage starts to slow down after I've downed 1.5-2 of the felhunters, and Kanrethad's DoTs begin to stack on me. I typically have to Unbound Will here, while using SacPact and Healthstone in preparation for losing control of the pit lord. When he comes at me, I pop Unending Resolve and run downward, just to the edge of my Demonic Portal range while using instants on the remaining felhunters. I teleport back in time to prevent a Chaos Bolt or Soulfire, and to give me time to either finish the felhunter or retame the pit lord.
At this point, my health usually stands around 65%, and I have one or two debuffs to cleanse, but all is good. Kanrethad predictably uses Cataclysm then summons the doom lord, which gives me time to heal, replace my portal, and deal damage. I banish the doom lord on sight and continue training the boss, while cleansing and teleporting incoming danger.
Whenever the boss summons the next wave of imps, I use the same process as earlier, while risking a bit more incoming damage due to banishing doom lord. This can occasionally be a tricky process, as I sometimes get wrapped up in damaging and banishing, and neglect to remove Seed of Terrible Destruction. This has, at times, caused the end of me. An ill-placed Dark Hole, while great for not breaking my armor anymore, is awful due to how confined my movement usually is in this encounter. Typically though, if I notice the DoT ticking low and I have no cleanses left, I'll either demonic leap in my pit lord's face for a cleanse, or demonic leap away so it summons the dark hole in a convenient location.
Around this time, if he hasn't already, my pit lord will randomly break free of my Enslave, and I'll have to lure him back to my corner, to gain control over him again. I have died a few times here, due to a very unfortunate Cataclysm where, despite my Enslave Demon finishing it's cast, the pit lord still isn't under my control, and the boss gives an unforgiving 1-shot.
If all is well, the imps will die, the doom lord will remain banished, and I'll be putting some consistent damage on the boss. His health is usually around 70% here, and I more-often-than-not successfully reach this point.
The next though, is where things get hectic. I save my infernal for an AoE stun on the incoming felhunters, while using my pet's charge and breath to lower them as fast as possible. I pop cooldowns and try finishing off the fel hunters, but they almost always eat my Enslave Demon at this point. While being affected by DoTs, Doomlord's bolts, and having a multitude of demons running my way, I shadowfury everything, pop my defensive cooldowns, and kill the felhunters. I typically have them slowed with chaos wave so I teleport back and regain control of my pit lord, while instantly healing myself up, as it's almost always necessary.
Sometimes, the boss will use another cataclysm before I can regain control of my pit lord (due to the time it takes me to kill the fel hunters), and I will die here at this part. Sometimes, I'll get an annoying imp that will get me stunned during my enslave demon, or a black hole that will knock my casts back, receive a failed enslave demon attempt, or some other unfortunate event that will cause the end of me, whether through Cataclysm or through direct damage.
Although that may be the most hectic time, it's not necessarily the part where I die the most. After the felhunters are dead, I feel revitalized, knowing it's only imps to come, but my hopes here are usually contrived and in vain. I heal up to full and cleanse the DoTs on myself, negating the harmful effects I had to take during the second felhunter phase through whatever means necessary.
Now, the boss's health can be anywhere from 47% to 60%, depending on how much damage I was able to get out, and how much the boss felt like getting friendly with my pit lord. I sometimes have to replace my demonic portal or create new healthstones, but most prominently, I'll have to use a purification potion to remove his end-all DoT. I will admit, I have occasionally been devastated, both literally and in mind, by forgetting to remove the DoT, whenever I've been progressing smoothly. On the other hand, I've made it to the end of the timer on his second end-all DoT and have gotten remorselessly killed during a good attempt.
After the second doomlord is summoned, I have to start juggling Fear and Banish, which seems to work alright for the cataclysm phase and the next wave of imps, but I can almost never get too far after the third wave of imps to come. Due to having to hard-cast Fear and Banish with 4% haste, as well as the occasional Enslave Demon, which has the possibility of being interrupted or simply failing, even with the glyph, I've fallen prey to an ill-timed cataclysm at this point. I've also had times where I couldn't cleanse a DoT in time, and have gotten killed by a dark hole or annoying imp, which has prevented me from successfully killing the upcoming waves of imps.
Due to the need to cast more, I'm not able to use my Demonic Gateway as often, increasing my threat, and the amount of attacks directed at me. Even whenever I do, it feels almost as if the boss is intent on killing me at this point. He'll still fire Chaos Bolts at me, even if I've recently used my gateway, which will cause me to teleport, and have to deal with singing/unbounding the DoTs, while taking the occasional incoming damage from the doom-lord and imps. Even if I heal properly, and shield through the imp damage, there's always the chance that I'll get a Cataclysm right whenever I lose control my pit lord, which seems to go off at 80% for me, instead of actually finishing the cast.
There have been times where I've had to be far too preoccupied with CC'ing the doomlords or killing the imps that I haven't been able to damage the boss enough, and have died to a second Ultimate End, there have also been times where my Hand of Guldan's didn't hit the target, due to walking or teleporting behind the pillar, and my pet's breath is less than effective, causing me to have to deal with multiple waves of imps. Sometimes, I'm too preoccupied dealing with imps after a mechanical failure like that and I can't dispel a DoT, like Excruciating Agony, which starts to deal massive amounts of damage. Sometimes, my Imp Swarms attack the doomlord while I'm casting banish, which causes the banish not to work.
I try, after this point, to use my offensive cooldowns on each new wave of imps, and to use my defensive cooldowns on each either enslave demon disappearing or whenever I lose CC on both doomlords, but whether it's the clock ticking, or what feels like my own mechanics against me, I can't seem to get the boss below 25-45%. I don't feel as if I can pump out enough damage, whether it's on the summons or the boss himself, and it feels like my spec, at least in this fight, is inferior to the others.
I've spent a lot of money, to me, on changing up my talents and performance-enhancing items. I'd rather not have to go destro, which would require an entirely new reforge, possibly new gems, new glyphs, etc. As well, I'd just like to be able to complete this content as my character is, not without the need for end-game PvE content, especially if I want to complete this fight with my specialization. At an iLevel of 477, and in full malevolent gear, it just doesn't seem to cut it in terms of damage, at least not with Demo. I'm not entirely sure if my mastery is even working for increasing the Pit Lord's damage, or if half of it is completely wasted due to using GrimSac.
I know I may seem stubborn, long-winded, and a plethora of other things you may like to mutter about me or this thread, but I'm trying-- hoping-- to find some sort of advice on completing this other than "roll destro", "wait for tyrannical", or "start PvEing". Also, for those of you who may question my credibility, please know this isn't my first account, but then again, a plea for help doesn't exactly show much credibility in itself, so I'm not exactly worried.
Regardless, thank you for reading, and I'll eagerly await advice.