Well, don't know what kind of DPS you are doing, here are my HoS strats:

Maiden: ignore her stupid spells, shadow resist aura + bloodlust = dead maiden
Krystallus: need to seperate your casters (with backs against some wall/rock), either place them at the maidens room and pull him there, or place them around his spawn spot with backs to some rocks (you usually get some damge with 2 toons, but not too bad)... other than that, tank and spank
Tribunal: kinda rough, am doing it like this:
Code:
    stairs to the chamber
             tank

shaman                  shaman

     druid       healer




    brann messing around
Am placing them like this so they dont get all hit by the lasers. Use fire resist aura, dont let any mob get past the tank, use consecrate and stuff to keep all mobs on you. Cleanse the magic debuff (100% dmg increase, ouch) and move toons out of the lasers. Needs some practice
Sjonnir: ignore his spells and adds, nature resist totem + bloodlust = dead sjonnir

That's with 30k+ health on the tank and 4.5 to 5.8k (crit RNG) bloodlusted DPS on all casters.