Temple of the Fist Second Boss problem

[Rymm]

He has a barrier up on three sides, if you attack from those sides, he counters you with a damage down debuff that is like 90% or something.

Yes, I'm aware. It's the 'Killer instinct' spell that I mentioned in my post. You only see the spell graphic of the barrier immediately after he casts it, the graphic fades a couple of seconds before the actual damage reflection shield does. If zooming back far enough to have a good view of the full boss doesn't work for you, then you might want to take the other peoples' advice in this thread and just stop attacking once you see the cast bar for it pop up.