So we had a warrior and a DK on him only
The DK used no diseases and no howling blast, noone else touched them, we didnt aoe the little ones but single target them.
His bar would go to the right side about half way, with both dps on his right leg full and then just suddenly drop down to a quarter again then back to 0
WHILE both dps are attacking his right leg...
We had more luck towards the end by having every DPS switch to him when needed, but it still moved soooo slowly and would randomlly decrease while nothing was touching the left leg