This guy was a pain in the butt. But using what people above have said, I equipped a Shock sniper rifle in one slot and a Fire one in another. I engaged him, and tried to find that ladder people spoke of. I was getting owned on my way there, and tried to hide around this corner by the gate leading into the area to regenerate my shield. He followed me, and if I was crammed far into the corner, he couldn't get at me.
I'd quickly poke my head out then back into the corner to make him pop up from the ground, wait for him to strike while I'm in the corner, after he does then pop out and fire a shot or two from my Shock sniper rifle to drain his shield, switch to my Fire sniper rifle and unload on him in the eyes like someone said above. Once I found this out, it was pretty easy -- I could shoot him, and he couldn't hit me. As you can see though it took a lot of rounds to do the job, I went in full and only had 5 rounds left, lol.
It would probably be just as effective with a gun with more rounds though, but those were the only shock/fire guns I had on me.
Hope this helps!
Edit: Just want to clarify that he could actually get at me occasionally even crammed in the corner, but my health was at 72 the whole time around the corner. The time between his hits still gave my shield enough time to regenerate, and it's a really slow one to regenerate too.