Health suddenly disappearing from bosses?

[Zefeh]

Yello, my guild has just hit 9 of 12 bosses on regular difficulity and because I'm bored in school I decided I'd post up a potential problem we found on the Twilight Councel the other day. It was our first kill(DK tank the only one left alive - 2k hp, closest kill ever) but there was a very big bug that the raiders reconized. We where in phase 2 with one boss at 40% and the other at 32%. We where just going to switch and balence out the health when suddenly the 32% shot down to 22% and we wound up entering phase 3 with healths at (22%,21%,32%,40%). Has anyone noticed serious server lag like this? That's around 800k-1mil health dissappearing in 2 seconds in 10man with 5 dps. Haven't seen that without any stupid buffs or is there an ability that inscreases boss health in this fight?

[Dunee]

the earth guy in that encounter has a shield that when broken deals 10% of the bosses health in dmg to him

Link to the ability: http://www.wowhead.com/spell=83718

[Deleted]

Edit : i was wrong sorry for wrong information

[Memoryz]

Just to repeat to the first reply. It's when he gets thicken skin off. It's NOT because of earthquake.

[Psychos]

When Harden Skin breaks he loses 10% HP.