Tyl regors sheilds

Stop trying to solo bosses that are way over your level, probably. Unformaed tigris oneshots him in each form.

I used Trinity, put up a Link so I always knew where he was (end of the Link thread) and I would run up to him and spam my Jat Kittag, with Berseker and Radiation Damage and each phase would last less than 20 seconds

Excalibur is his bane, really. If you build an Excalibur decently, his exalted blade will take out each phase in two seconds. Unless you let him smack you with his axe, then he can stagger you to death. So, don't let that happen.

Or equip a mod that adds Toxic damage to your gun or bow, it ignores the shield and you can wittle him down if you're accurate enough.