We now have 38 attempts in on H LK 10m. I can confidently say that we make it cleanly into P2 75% of the time now (based on the last four attempts), but it's far from easy. As it should be, this is the single most difficult thing I've done in WoW. Here's how we're working on it.
Phase 1 - the kite and scream
Phase 1 introduces the Shadow Trap as another mechanic that will instantly wipe your raid. Similar to a Defile, it has to be dropped behind the raid as you kite the LK and his cronies from the steps to the edge of the platform. Moving as little as possible helps here, as you can quickly run out of room.
For positioning, we have the LK and melee on the left - moving from pillar to pillar (Stairs to teleporter pad area). The ghouls and horror tank are just to the right of the LK tank, with the ranged and healers to the right of that. This positioning has worked fairly well, though there are occasional accidents involving Shambling placement.
Raid setup is Feral Druid on the LK, Protadin on the adds - Holy Paladin and Disc Priest healing, and six DPS (so much damage). It's not uncommon for the LK to have 25k+ hits back to back on the MT, and it can be a challenge if Mongrr or I get hit with the plague.
Right now if Mongrr or I get picked up by a Valk, and there is an infest, someone is going to die. At one point we had an infest out, soul reaper, Valk, and a defile. I'm pretty sure Golemagg showed up on that attempt as well. Our best shot so far was about 50% before the proverbial wheels came off.
H LK is another fight that gives me everything I could hope for. Insane damage, personal responsibility, tight group dynamics, and it truly feels like the pinnacle of Wrath raiding. I fully expect that we'll have it down in another 30 or 60 attempts, though we're going to have to do some more drake selling or GDKP runs to cover the costs.