Ok, here is the tactic we used in our raid group (we also 2 healed it), we had the tank with the most add control taking Horridon on the first gate, (would probably be the warrior in your case), then after the first gate tanks would swap, and the other tank would keep tanking horridon until the final phase (clearing debuff with HoP after each gate closes). Also remember if you get charge on you, move to the tank / tail of Horridon, we found this to really mess the fight up if someone didn't. 1st gate:
All dps will focus down the first special add that jumps down, he should die right around when the 2nd pair jumps down.
Then after that the 2 other adds will jump down, mark one and burn him down first, then swap to the other one/the Dinomancer.
Pick up the orb as soon as you can, be found that it really didn't matter who did it, have the Horridon tank pick up the remaining adds, do the tank swap, and kill the remaining adds, then do some dps to horridon while moving towards the 2nd gate.
Have all dps nuke the first venom priest as soon as he jumps down, he needs to die before the 2nd pair jumps down (remember to interrupt, we had out hunter do this, but anyone should be fine).
Then when the 2nd pair jumps down have the horridon tank pick up the add that is closest to the 3rd gate, and have him interrupt the venom bolt.
The other tank and all the dps will nuke the Priest closest to the 1st gate, he should die rather quickly, then he have all or dps swap to the other priest, while our add tank and rogue stays and waits for the dino, then when he spawns the tank and rogue nukes him down, and the rogues takes the orb.
you should have zero stacks of poison.
After the first frost lord jumps down, we uses army of the dead of heroism, and nuke him, while tanking him right at the gate.
Then when the 2nd pair is just about the spawn, the tank places himself where the add closest to the 4th gate is going to jump down, so he can quickly do an AoE on him and get aggro, then he tuants and mark the add furthest away, at this point dps is holding back and killing the small ones, once both the frost lords are at the tank we nuke the marked ones, and moves slowly backwards towards the 4th gate everytime they spawn an orb.
When the dino spawn, he have a range interrupt him, and the tank tuant him into the group, the everyone Changes to him and nuke him to 50%, grab the orb and close the gate as fast as you can.
Kill off the remaining adds before the 4th gate opens.
Remember to have everyone that can dispel do it when they can.
Tank needs to be really fast at picking up the bears, as the can kill dps/healers really fast.
We nuked the first bear and shaman as fast as we can.
When the 2nd pair jumps down we let the tank get aggro on both of them, and just nuke the normal adds meanwhile.
The dinomancer should spawn before you kill any one the bears, then we swap to him and nuke him and close the gate, then we finish off the Bears/shamans, and move Horridon in the middle of the room.
We do a tank swap so the tank without any stacks take horridon, we then nuke horridon (but save your CD's) until the War god jumps down.
We then swap to him pop all cd's and nuke him down, then when the other tanks stack fall off we do a swap, and everyone else just stacks on the side of horridon and nuke him.
It looks like you're getting through the trash phase sometimes. DPS output looks low, but this is mostly because you're not getting the full benefit of the boss damage debuff because you're dying before he does.
The first phase is not about pew-pew, but survival. AoEing everything down should only be done once the dangerous things are out the way. Venom Priests, etc, should be single targetted.
There are also big hits in that latter phase, and one of our tanks is very squishy there too. All healing focus should be on them, make sure one healer is watching each tank, with the third putting heals on both. If you let them do their own thing, you'll find one tank goes low, both healers scramble to land big heals on them, and while they're doing that the other tank dies.
I really don't understand why any priest would chose to be holy on this fight. Went disc on this in LFR and did 134k dps (I'm shadow MS so haven't tried it in a real raiding mode). While it would obviously be lower in normal mode due to dispelling and actually having to pay attention to rapture, it should still be tons of free dps and cheap heals.
You did 40k higher than the highest ranked disc on WoL? Not like it matters at all, but I'm calling BS.