I've been levelling my first ever character (the lock) and been swapping through the various specs to keep things interesting.

She's 79 now, but I was questing in Zuldrak and soloed the ragemanes flipper quests at 77. Ragemane is a 75. No real special abilities that I could tell. My felguard was able to tank Ragemane the entire time.
I would just dot up ragemane incinerate a little, then heal up the felguard no problem at all.
It took a while but my felguard was never in any real danger and I was able to life tap and drain life to get mana back.

I also took downa level 80 elite at 77, but that was one of the huge trees down below dalaran (the red ones). I got an add in the midst of it and it was a piece of cake.

Both elites aren't exactly toughies - but bearing in mind this is one lock with no healer and I think your 4 warlock +healer team would do just fine on a lot of elites.