Lady Deathwhisper, like Thorim, is all about the first phase. Once you have that down, the second phase is relatively cake-like.
…please note that I’m only discussing the 10 man version, because that’s all that I’ve seen. I don’t want to contemplate MCs, too!
A priest putting up Shadow Protection can help take some of the sting off the boss’s random shadow bolt chucking, though a paladin probably wants to keep imp devo running even if you don’t have a priest.
Don’t stand in death and decay!
Floaty ghosts called Vengeful Shades are for OMG GET AWAY GET AWAY. They go asplode.
When we tackled Lady D, we had 3 melee and 2 ranged. Putting the ranged on the boss and the melee on the adds worked fine for us, but you may have to adjust depending on raid comp and who your heavy hitters are. Some people have all DPS switch to the adds, then back to the boss. Pick your poison.
The left side will spawn two melee adds and a caster. The right side will spawn two casters and a melee. Split your tanks as best you can-we had pally left, warrior right. Left’ll spawn first. Every so often Lady D will empower a mob. The big, ugly hulk looking things some of them turn into hit like a freight train! Rotate cooldowns if you can to give your healers a break when those mobs are out. You can kite them, too, but we actually found it easier to stand there and rotate cooldowns. The reanimated skele dudes (Adherent) don’t hit quite as hard but are still a priority. Of course they are also immune to physical damage. Have fun with that.
One person should run over and be ready to pick up the boss just before her mana shield pops. She has a threat reducing debuff that will have you swapping tanks every couple of stacks or so.
Kill the things you are told to kill (depends on if you’re splitting DPS or burning the adds). Pay attention to the magic/physical immune reanimated mobs.
Kill empowered and reanimated things first.
When the boss enters phase to, HANDS OFF until your tank is ready. Be mindful of your aggro due to the debuff put on tanks, which lowers their threat generation.
Have interrupts ready for when the boss casts frostbolt. Frostbolt is fail.
Make green bars full.
In the first phase, beware Big Green Ugly Hard Hitting Mobs of OW.
Watch your raid frames for the Red Square of Someone Made A Mob Angry around someone other than your tanks, because someone somewhere is going to aggro something they shouldn’t have while the tank is cussing and trying to finangle multiple caster mobs into position. It might even be you. Damn healing aggro.