Blood Prince Council Hardmode

The major and HUGE difference in this fight is a simple yet incredibly annoying one: Whenever your character moves you gain a stack of a DoT debuff - it does 500dps per stack, and is refreshed with each new application.  It has a 10s duration.  This means, if you stand still for 10s all your stacks drop off.  This debuff HURTS.  This debuff is applied not only when you run, but also when you get knocked back by anything in this encounter that knocks you around.

So, this encounter now becomes even more about positioning and team work.  Due to the Vortices and the need to be spread out, and also due to the need to Not Move, it behooves the raidleader to plan out where everyone is going to stand as their "permanent" position.  A good idea is to space the healers around the semicircle at the bottom of the stairs with one healer at the top of the stairs to keep those on stage alive due to LoS issues.  DPS need to stay spread around the room.  Melee should be allocated spots on the top of the stage for the personal vortex phase.

Tank both Taladaram and Valanar as together as possible to minimise melee movement.  The Keleseth tank will need to move around obviously, so the healers need to be aware of the stacks on this tank (as does the tank themselves).

The kinetic bombs drop significantly faster in hard mode, and also, you cant allocate 1-2 ranged to go after them as you just dont want people moving around.  Allocate a spotter to call out where the bombs are falling (we actually use a mut rogue due to their reduced damage from all the target swapping and moving) and anyone in that area has to stop DPSing the boss and keep that bomb up full time until it goes away.  If the bombs drop on stage, melee need to be allocated to hit them (in this case, our mut rogue generally handles the entire stage on his own). 

If you do get knocked back from a vortex or kinetic bomb, run back to your position in stages to ensure you dont get too many stacks of the debuff.

Even more than in normal, this fight is NOT a DPS race, I cannot stress that enough.  This fight is about staying alive and whittling away at the boss slowly.  There is a stupidly long enrage timer, you are very unlikely to hit it, no matter how long you take.

The key factors are: Staying spread out and staying in your allocated position as much as possible and making sure those kinetics do not touch the ground under any cirucmstances.  It is everyone's responsibility (except perhaps healers) to keep a kinetic up in their area.  If a kinetic touches the ground near you and you didn't hit it, then the resulting wipe is 100% your fault.