Order? Hell, I just w-summon KOTR+mime and his ass goes down. Then I use de-barrier, w-summon+KOTR, mime and omnislash if necessary and Safer Sephiroth dies too. 'course by this point, Cloud's at level 93 and the others in the mid 80s.

But even the first time I beat him I didn't try any order; I just focuesed on one body part at a time and healed when necessary. I never found him that hard, really, just very persistant and long.