I've started boosting four of my five man team with my main (a level 70 warlock, demonology specced).

At least in Ragefire, its working very very well. My pulls are based on the maps on the first page (generally) and I pull with the felguard having him attack a mob and move on, finally going "passive" and following me back to the party. Once there I have the pet stay in place, back up and cast a single seed of corruption. A few seconds later, mobs are all dead. (I usually get myself into melee range as the dot effect of the seed can pull the mob off the mass.)

I'm curious to see how well the felguard will hold up in SM with this strategy. Even in Ragefire if I let the mobs beat on the felguard enough, he gets beat down. May switch to voidwalker.