This is with a 540 defense warrior, 3x Elemental shammies, 1x Resto shammy. Successfully cleared Gundrak heroic 3x without wipes.

1.Slad'ran - Serpent boss - pretty much tank and spank - keep your casters at max range or the venom AOE will wipe you. I used elementals and thunderstorm on the adds. I DPS'd thru the 'cocoon', YMMV.

2. Drakkari Colossus - Elemental boss - Stone form is EZ. Save bloodlust for Elemental form. When he goes elemental, Ignore the puddles, they do minimal damage. 4x Healing stream plus a chain heal once in a while will take care of it). Also, split up when he starts barfing as he will charge through your guys. He will go back to the tank so don't bother trying to reposition targeting (as he ends up behind you when he charges). Also, when it seems like you've killed the Stone form, he will go back to Elemental once last time.

3. Moorabi - tank and spank. Try to interrupt his transform. Get ready to mass chain heal when he does the quake.

4. Gal'darah - I had trouble with this guy the first time. His knockback is annoying as a multiboxer (it also hits sideways). What you should do is find a corner where you can wedge your guys (where the Rhino mobs are before the boss is a good spot, by the torches on the side). Make sure your guys are wedged in so they can't move sideways or backwards. Pretty much tank and spank - max range in human form, group up in Rhino form - have your tank come to you. Spam heals on the tank and chain heal if your others need healing.