Basically I was in demo form permenantly.. you can see my gear level by looking at me but on this toon, i had 71K armor, and 170K HP.. I used the talent to sacc your pet for 15% HP and damage and I had 184K HP. With my mastery, and the glyph for reduced damage it said i took 51% reduced damage.
Demon Soul (our current cooldown with a per-pet basis) is now per-spec.. and the demo spec gives flat +30 mastery for 20 seconds every 20 minutes. I would pop this and have 117% reduced damage taken. I glyphed my healthstone to do 40% of my max health over 10 seconds
(side note.. healthstones now have 3 charges like mana gems for mages and do 20% of your health by default). The twilight ward transition spell isn't really that great of a mitigation because you have to channel it unfortunately but I could good in a pinch..
Since wands were removed from caster classes, the demo form auto-attack (which you can still use at slight range) is basically throwing shadowbolts with both hands.. it looks awesome! I have 4 AoE abilites, and curses turn into auras.. aura of enfeeblement applies to everyone in 20 yards for 30 seconds, doing reduced physical damage by 30% (the same as the curse regularly).
Using all of this, I was able to solo heroic stonecore as a tank.. Since addons currently aren't enabled, I wasn't able to see how well I was doing but things died really fast (i don't think I could solo the twilight heroics though).
ONly problem I could see is that none of the spells have tooldowns that say "generate high threat" or anything so im not sure if they just haven't added that or what since no one will let me tank for them :'(Our abilites:
Demon slash - does 30K damage for me (approx).. no cooldown, just the GCD.. generates fury
Soulshatter - now a taunt with an 8 second cooldown
Corruption - costs fury to cast, but generates fury per tick. autoattack refreshes this
bane of doom - still the same
2 auras (same as our 2 curses)
hand of gul'dan - this is new.. it's now a charged base spell.. meaning it generates a charge every 15 seconds, with a max of 3 charges so you can use all 3 of just 1-2.. you can instant cast all 3 (with GCD) and it's target like RoF, not your current target. this could be used to get initial aggro on groups and generate more fury. each hit gives the targets a 30% speed debuff that stacks (to 90% movement redux)
Immo aura - our hellfire morphs into this.. it is a HUGE ranged aoe that pulses around us. lasts for 10 seconds, does a TON of damage (like 15K a tick) and doesn't do damage. it does cost 450 fury out of our 1000 but it isn't hard to get fury at all
Shadowflame - this is the same except that instead of attaching to us, it stays on the group and shoots it, but drops it at your target location.
demo leap - just a jump, but still can be used to close the gap or charge in for positioning
then our tank cooldowns.. twilight ward turns into a 30% damage redux with the damage taken doing demo fury instead to 1% of your health but doubling the fury taken every 2 seconds.. it's kinda weird i don't use it. have to channel it but the graphic looks cool. lol
the 50% damage redux
the 50% self heal and 25% +healing (could get a different heal talent). this is 50% of your max health over 20 seconds since we don't have soul harvest anymore.. this is soul harvest but in combat.
immunity to damage for 10 seconds, then 50% of the damage taken while immune is done to you over 10 seconds or something like that, not really looking at the abilites at the moment, just recalling from last night.Like i said i was able to solo stonecore but i couldn't really test out how i hold aggro against say a fury warrior or a fire mage or something.. searing pain is gone :( (they let us tank and take away our high threat ability >.< )
can't queue tank yet.. but i would be interested to see this expanded upon.
sorry for the long post :PPS. Soulstones are now castable and don't have to make an item, with a 10 minute cooldown and a glyph to make it 100% like druid rez!! woohoo!! :D