OP back again here.
I managed to get some LI runs going (well aiming for my weap but no success :P) and used the advice here...
Basically the keep strafing part. I noticed that, even when there was NO<- yellow circle under my feet, I did receive damage from eruptions underneath. I guess the first boss is bugged when it comes to that part?..
It sounds like you are talking about the Shaclaw. If that is the case, I suspect the issue is that you got hit by a graphical bug where you are actually standing in a invisible yellow circle. You take damage as though you are in one but low and behold it's not there
Guess the first person commenting on that bug was right. In one of the last fights I did in the last 2 days, one of the party members died by that damage while not standing in yellow circles as I paid attention to everyone in that fight. I was like waddafuh. I kept strafing and pretending that eruptions without yellow circles were just those yellow circles and it was as if I didn't even need a heal.
On the subject of using Mind Control.. I do not use it unless I am losing aggro (like someone here said Shadow Tanks have great threat control and I don't have problems with it) or if I know a boss does AOE damage.