Got this down on my mixed team (prot pal, resto sham, 2x arcane mage, dest warlock) with help of the suggested strats in this thread.

First boss:
Easy if you dont mess up.

I tank him down in his room with my team standing almost at the bottom of the stairs. I found it easier, for me atleast, to switch the healer window to main after placing the mob where I want it cause fight is all about dispelling the nasty DoT and interrupting and healing the team after he brings you down to 1hp. Until his archangle phase (at appro 1 mil HPs or so) it dont matter much if team is banged up as long as hey live.

I save burn for after the last time he brings you down to 1hp and before archangle phase. Pop cooldowns, heal up the team and burn him down.

Second boss:
Easiest fight in the dungon imo. Tank and spank with paus for killing the adds. Can leave the add at 25% up.

Third boss:
Tricky fight with annoying adds.

My strat is to place my slaves in the inner right hand corner as you enter the room (or spread them out along that wall). I tank the boss i the middle of the room so that my toons are out of range from the desecration AE thingy. When adds are about to spawn I place a consecration at one door and move to the other to pick up that add and then bring boss plus the adds back into the middle of the room. Rince repeat loot.

Fourth boss:
Easisest strat form me is to ignore the cold poison phase. I spread out my slaves along the wall as you enter the room so they all dont get hit by same ice pool. I try to avoid the ice pools with my tank. You probarbly will have to overgear it a bit to be able to ignore the ice pools.

Jump for poison phases and quick dispells/cures of the nasty poison dot.

Last boss:
This one is easy in theory but it had me pulling out my hair mostly because the stupid arcane missiles misaligns my mages so that the strafing strat was a bit hard to execute, toons where all over the place after a bit.

Even with DBM I found it hard to see when he starts casting Pistol Barrage, ended up having to zoom in more than I like to be able to spot his turning.

Started out tanking him at the bottom of his stairs with toons place so they could strafe to their right behind the wall there.Tank was placed opposite the toons facing them. That worked for a few barrages then I had to reposition using /follow and keeping boss between tank and toons and just run forward with either tank or toons at the pistol barrage. Adds I just AEd down.

Is a bit iffy at times when tank has the healing debuff.

Thinking of switching mages to fire or frost for this figth for ease of movement, or just kill the DPS macro on the arc mages and just spam Arcane Blast