Hunter Guide to Karazhan bosses
For the most part, hunters have it easy in Karazhan. Nothing frenzies, you don't have to pull, and only one boss fight might require you to kite. This guide / cheat sheet only covers hunter-specific things to the boss fights. I'll assume you'll find the general strats elsewhere.
General Note: Do the most DPS as you can without pulling aggro, FD often, don't forget to use all your cooldowns, and turn off Growl.
Attumen the Huntsman & Midnight
When he merges with his horse, stand at minimum distance behind him, pewpew, and go afk. You might have to trap some of the mobs clearing to the boss.
You may be asked to trap one of the adds. I start at the right of the dais Moroes is on. Drop a trap, peel off my add with distracting and arcane shot and trap it. Move a few to the left and drop another trap and move a little more, so he'll hit the trap coming after me. If the traps are resisted, missed, or don't last long enough, wingclip, concussion shot, and/or scatter shot to get some distance to try again. Try not to drag your add through the healers...
Don't put your pet on the boss unless you have 2 pieces of t5 or very generous healers. Before she does Repentance, use The Beast Within to keep DPSing while everyone else is stunned.
No matter what encounter you get, it's all the same pewpew.
Pewpew, keep your pet out of the charred earth, stand at max range and strafe out of charred earth yourself.
Pet on the boss, you kill the arcane orbs with the rest of the group. When he evocates, hit every cooldown and WTFPWN!!!1!
Kill order: Demonic Chains, the imp, Illhoof. Open up on Illhoof when the imp is dead (he takes more damage).
Watch out for where Blizzard is starting and don't get hit with it, it circles the room clockwise. If you're targeted for a spell, FD. When he sucks you in for Arcane Explosion, put your pet on follow when you run to the edges of the room or bye bye pet.
Hope you get the blue beam! I've hit over 20k DPS in it. If your group runs during the banish phase like mine does, you don't really need to have your pet follow you. He's never killed my pet and usually he'll just unsummon from the distance.
I always get a pawn :(
Pets should only take damage from infernals, so should never take damage. Stay with the ranged group.

