I want to try this strategy now that we have two pallies 

Paladin Strategy
Requires 
2 paladins to aoe 
Advantages 
Being able to do it whithout a warlock 
Faster to do 
The paladin 
At the spawning spot of the little imp a paladin will need to stand. 
Both paladins should be in the same group and have Fire Resistance Aura and Concentration Aura on and buff the other healer whith Salvation but not them selves. 
The paladins must keep consecration on the floor there while having righteous fury on. 
This way the paladins will be the ones who get aggro and get damage. Let the paladins heal each other so they get mana. 
If you got a mage Dampen Magic will be great on the paladins. 
The paladins should heal the tank and each other, let 1 other healer focus on the Demon Chains. 
Imp killing 
After a while, when there are too many imps let a mage or warlock AoE all the imps down. So there will only be 2 again from the spawn. 
This way the AoE'er only needs to AoE 3 or 4 times or maybe less, this way it will almost cost no mana to kill the imps. 
Rest 
Let 1 tank tank the boss. 
All the other people can dps on Kil'Rek, the boss and the Demon Chains. 
The dps should always kill The Demon Chains first, after that the imp, and if those are both gone you can dps the boss. 
I came up with this tactic because we didn't have a warlock and our mage got oom. 
signed: Inoué guild: Order of Rotheran server: Trollbane


Kanna is also speced for this strat which sounds like it could make the fight fairly cake and make me look great on the dps charts

[edit] Using a Mage Instead of a Warlock 
This requires a Mage specced with Magic Absorption, Burning Soul, and around 300 Fire Resist. You will also need a Paladin for Concentration Aura. Note that if your mage can't reach 300 Fire Resist on his own, you can have a second Paladin, or a Shaman use Fire Resist Aura/Fire Resist Totem. 

The strategy is simple: the Mage starts using Flamestrike repeatedly on the center much like a Warlock would use Hellfire. Since the Mage will be resisting most of the imp fireballs, he or she will remain at 100% mana for the duration of the fight thanks to Magic Absorption and can continue to AoE with wild abandon. 

The Mage can also dive in with Arcane Explosion if the DPS from Flamestrike is not killing the imps fast enough. Mana should not be a problem at all with enough Fire Resistance.