Dipped my toe into Marilith. It isn't a clean sub 30 as it reguires some luck for Yuffie to not lose shadows or Tidus to be targetted two times right now for SB gauges...but it is a clean ~33 seconds clear with a best of 26 seconds.
I think getting into a rhythm of who to entrust with OK and when would make it a clean sub30. Entrusting Relm twice at the end seems to perform better than 1x Tidus and 1X Relm.
Spoiler: show
Edit: Best time down to 23 and change. Really, if Yuffie doesn't get hit by a physical attack after her USB goes off around her 4th action, the run is sub 30. Love it.
Now if only some Firemanes would drop.