Hans'gar and Franzok’s Crippling Suplex ability no longer deals damage based on maximum health of the tank who was picked up. It deals a flat amount of Physical damage to both tanks who are thrown together. (200,000 damage on Raid Finder, 450,000 damage on Normal, 600,000 damage on Heroic, and 700,000 damage on Mythic)
Known issues that will be fixed in Patch 6.1:
When grabbed by Hans’gar or Franzok in advance of Crippling Suplex, tanks are currently unable to use abilities. They will be able to use abilities while grabbed in 6.1.
http://us.battle.net/wow/en/forum/topic/16201250882
Looking at logs thats exactly the damage I take if I remove any defensives used and passive DR from blood pres. Exactly 700k x the % dmg buff they are at(which builds up the lower HP they are). I also looked at all 3 of my tanks logs. Both tanks in each run all take the same damage. We have every kinda of tank except a bear combined if you count all 3 runs. The damage intake is 100% the same around 715-720k for first one, 730-735k for 2nd one and around 750-755k for 3rd. Obviously damage intake will vary a little due to the percent of the boss when it actually finished the cast(main raid pushes them stupid fast).
It has never been % HP except for that day and a half before the hotfix went in.
Otherwise both tanks wouldn't be taking the exact same damage before passive DR/Externals. It would look really skewed with blood dk who has over 800k constant hp vs a 450k hp monk.