take away his focus and he self-destructs. on psychological just cast sacrifice on your friends, they give you several rounds of thousands of hitpoints and the baron wastes his focus trying to destroy you. use retrograde after he starts losing points, and sometimes you don't even need to hit him.
I do agree. In the beginning of zone 4 in Sonny 1. I equip all my team with his armor by go back to zone 3 and beat the crap out of Galiant until I got 6x6 of all his armors before I go to training in zone 4.
And when I have enough money, I bought all the necessary armors for me and my team.
As a hydro, use regulate (near right side of skill tree), as a bio, use disrupt (near left side of skill tree) and as a pshyco...
Use haunt and perhaps shock coma (was that the one?), when he gets down to VERY low focus, that the next move he makes will make him do deep burning, try to line up dark echos and overdrive to both be in effect, you will pretty much completly take him out.