Concur with above post. It's much easier if you're with friends. And have Maya's phaselock to kill those healing bots it spawns. Take down the things shields with electric and corrosive. Keep hitting it near that red eye thing. Sniper guns help. I just beat the thing with my bf.
The best and the easiest way to kill him is when it flews to friendship gulag...there is a place on the right hand side where he's standing..jump right into it and then its way easy..u won't be hurt by any of the robots it generates and even from the renforcement....all u need is bullets and cash to buy them if ur out of ammo...
The best way to kill him if you have no corrosive/shield weapons is to run right up close to him and spam your most powerful gun into his face when his shield is down. You will get killed but during fight for your life, just kill one of his minions and spam bullets into its eye again. Rinse and repeat until dead.