My friend and I fought the Badassasaurus at 61 yesterday and it was the worst experience we have ever had in the game. You cannot fight that thing properly in UVHM or you will kill yourself with reflected gunfire. After we took out all the crit points I noticed that every time I shot my Lyuda at it there was about a 70% chance it would nealy kill my shield and if it corroded me as well I was dead.
In the end we had to spend torgue tokens on Torpedo ARs from the vending machine because it couldn't reflect those back at us. WIth all its special attacks gone is was barely a threat at all if we didn't shoot it with normal guns but my god it was boring trying to bring the rest of its HP down.
Use a homing meteor shower or bonus package he isn't resistant to explosive damage and you can keep refilling from the ammo machine 8 grenades at lvl 50 took him down to almost half for me, explosive relic makes it faster