I know this spec inside and out. I know how it works, how it doesn't work, and its strengths and weaknesses.
As of right now, the disc spec has been absolutely GUTTED.
During cataclysm (and wrath) discipline priests were tuned to use mana faster than other healing classes in order to push out the same amount of heals. That worked because discipline priests relied on rapture for mana regeneration. My mana regeneration in cata was routinely twice that of any other healer in my raid group, and my heals were roughly competitive (sometimes higher sometimes lower, as it should be). (We cleared heroic DW just before the 30% nerf--which was good for our guild. We take a fairly relaxed view on progression.)
The int>>mana pool>>>rapture mechanic was THE CORE of discipline play-style, because there was no other way to maintain mana with the high rate of consumption necessary to keep up. ...But it worked, because you could scale output and your regen scaled with it... it was NECESSARY to keep up.
In MoP, not only did discipline lose the core mechanic that had sustained it, it also lost divine hymn (our only big healing cooldown). ...Mana costs were not reduced in a relative fashion, nor did we receive anything to compensate for our lack of output cooldowns. ...In fact, all we really got was spirit shell (great situationally but not spammable in most fights. -- OK utility but NOT core.)
So how do you compensate? The ONLY WAY to maintain mana regeneration now is to SMITE HEAL, which has always been mediocre to terrible for throughput.
Since MoP I've been hoping and praying that I just hadn't learned it right... That maybe, somehow, if my play improved enough and adapted enough, I could overcome.
I was absolutely wrong.
Discipline (outside a 25-man raid, with which I have no experience, and which relies on different mechanics) has been absolutely destroyed.
As of right now the ONLY way to even remotely keep up with other classes' heals is the following rotation:
PWS > Penance > Holy Fire > Smite, Smite, Smite > Archangel > Power Infusion > Spirit Shell >> Spam PoH.
Do you have ANY FREAKING CLUE how ridiculous it is to try to maintain this complex a spell rotation while trying to effectively heal ANYTHING???
If you deviate from this in any direction, either mana goes out the window extremely fast or heals fall off to 60-70% of what any other class is capable of.
There is NO flexibility and NO power behind this spec anymore.
I can see three possible "quick" fixes.
1. Double the mana regeneration from rapture (at minimum. Or, better yet, make it scale from OUTPUT again.)
2. Halve the mana cost of all healing spells. (Taking off 1/3 might be enough--maybe.)
3. Double the healing quotient on smite/penance/holy fire so that it heals double the damage done.
Frankly, I don't think any of these really address the core issues, of which there are two.
1. Spells cost too much for the regen we have -- We can't compete with others' output.
2. Smite healing throughput is total shyte. TOTAL SHYTE. It always has been.
Between these two issues discipline is destroyed with the current core mechanics.
Frankly, I find this to be an example of the spectacular brand of incompetence I've come to expect from the developer community at Blizzard. Every tier, I pray that they won't touch anything to do with my class because they keep breaking things in such amateurish and ridiculous ways.
I AM A GAME DESIGNER. I KNOW OF WHAT I SPEAK.
If the team responsible for the ridiculousness that is discilpine in MoP were my employees, I WOULD FIRE THEM.
If this isn't fixed in the next month, Blizzard WILL lose my subscription.
I kept playing for friends so far, but that only goes so far.
This is just stupid.