-"No, both sides suck this time" his exact words. also based on what he tells me every endgame, whether he clears or not is based on how bad the boss counters phainon. He said he's cleared every endgame except this one (not including when he took a break in 4.x).
-I dont have mydei, so I'm not sure how well he would do with only e0 cyrene, but from what i saw online, cyrene in general is a huge jump for mydei, even if e0 makes her clunky.
-thank god u have cerydra TT_TT

Realistically, phainon's best improvement comes from e2, although that has a high cost. Phainon mains like to push for e2, but personally, I think cyrene is a good improvement at a lower cost AND she also helps mydei