Well, my mod ups the damage of weapons, but not enough to unbalance the game in such a way. At least, that's what I always thought. I certainly thought that robot was tough when I fought it. I was even using Zeta Weapons. I could never kill it faster than it could kill me, even with T3T in effect. I had three energy weapons, 1 a Zeta, two vanilla uniques, and 120 stem packs, I remember one of deaths I was pressing the hotkey rapid fire for stem packs and shooting the damn thing with the Zeta Pistol, I died in 5 seconds, max. I wimped out and used Robotics Expert.
It sounds like it's working as intended in your case, and I'm glad to hear that Zeta weapons didn't turn it into a joke for you.
I'ma repeat, though, it's possible to kill it predictably and reliably with any class of character. Think of it as like a puzzle for people who like puzzles - or, a necessity (aside from console 'kill' command), if you don't have that robotics expert perk. hehe.