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.