The trash mobs in the zone can be a bit of a pain in the butt. The Lair Brute have to be fought like Huntsman in Kara. Get right behind them and just into Ranged distance. They will charge like Huntsman and let your tank get in position before starting on the DPS. The Gronn-Priest aren't bad from a hunters perspective. Just DPS them down. There will be 3 random trash mobs before you get to HKM.
Being a Hunter you will probably be Misdirecting a mob to an offtank. There is also an add named Kiggler the Crazed that is usually taken down by the Hunters and Boomkins. I have not tanked Kiggler so can't supply and first hand knowledge atm but once I do I'll update this section. He does Lightning Bolts, Polys, has a knockback and threat reducer.
Find out which tank you are MDing which mob onto. This is a time where the focus MD macro thats in the macros section of this blog works really nice. Once that is done you will either go straight to Kiggler or to the first add in the kill order your raid has decided on. In the video below we did Seer, Olm, Ranged on Krush, Melee on Kiggler, then HKM. (once i get the video uploaded)
When you see this fight for the first time it looks like total madness but once you get the hang of it it is actually a very fun fight.