Just in case anyone else didn't fully understand the "kill some of your party" strategy, the key is to have them die before the first transition.

I must have been really slow witted last night, I thought it meant let them die IN the transition, but that still left all their shadows and I always wiped.

For me I found a nice balance with my pally tank and 2 shammies. I now send in 2 party members to die before I pull the boss.

And in case this will help others, here's how I do the last fight:

  1. Engage the boss, pop Heroism (Blood lust for you horde)
  2. DPS like mad
  3. Transition starts
  4. I hit my Fire Ele button on the shammies
  5. My pally is my main window, and I kill the shadows Ihe has
  6. My shammies self heal as needed while the pally is busy
  7. Once the pally's shadows all die he gets to see 1 of the shammies and that shammies shadows
  8. Now the pally and that shammy kill the shammies adds, with the shammies continuing to self heal as needed
  9. Once those adds are done all 3 party members can now see each other, and they all kill the last shammies adds.
  10. After the last shadow dies the boss re-engages
  11. Repeat until boss dead, there should be 1 more transition phase