My decent Wind team (All SR's + Cu Chulain, 32k power) is able to auto-kill Ixion Ultimate if I take a +50% damage eidolon with me. If I don't it takes some hand holding. Was able to MLB the weapon by Saturday morning.

I was doing Expert Yatagarasu with an all SR dark team. But then I got Raiko out of the gem gatcha, so I switched to my Thunder team with comparable power to my dark team (now all SR's + Raiko, currently 26k). I'm at the point where I can auto-kill Expert Yatagarasu if I take a +50% or more damage eidolon with me (after switching to start off hitting Will O The Wisp). Otherwise again, hand-holding and hoping I get healing items from the trash mob. I'm finding that I actually need Yatagarasu to go raging before I let her get her Ultimate off or else my team is facing 5 turns of putrefy (which is just death for me, as I rely on healing).