I just did this fight today on 90 NIN, (and 90 WHM, I main tank and main heal myself, cause Im a champ) it was so easy (except when it silenced me while I was casting migawari, and I couldnt find my silena macro and it 10k needled me while I wasnt looking and didnt notice my migawari wasnt actually cast!)
I haven't been to Odin in forever, and some stuff is very different now. Some of the things I saw recently asked were things we tried, like at 11% I recast utsusemi, used blade Hi, then disengaged, and /heal, that instadeath move it does only did like 300 damage to me. Migawari kind of feels like cheating for this though lol, it's that good. Actually tanking it is pretty easy too, as long as it doesnt spam aga spells at the exact wrong time, its very easy to not get hit at all, using DD gear, not evasion gear. We also came to the determination, 2 good ninjas with marches and haste is all you need to very easily kill Odin now, we messed up and our bard couldnt enter (lack of t2 feather.) we had 8 characters, 6 players, and no where near an ideal setup lol. It was WHM+WAR for 1 person, NIN+WHM for me, NIN, RDM, SMN, and BLM. It was so easy, I couldn't really believe it.
Did you do T1-3 beforehand? If so, how was that at 90?