So after changing the way I did a number of things, I'm still running into the core issue that at some point during level 4 it just becomes a meat grinder and while I can usually get to the boss at 5, unless I get a girl with 100%+ dodge (which happens extremely rarely as dodge % seems to be the rarest thing to get, let alone be able to stack it on a single girl.) I just can't beat the last boss without using a heart.
In general I take the top 280 by power and make sure none of the top 7 have skills. I take a low skill heal team as far as it will go, hoping to get a good dodge and then it almost doesn't matter what I do after that. I have tried high skill teams using heal/mana/shield but they just end up getting wiped against a red team at some point and then that strats over. I'm choosing the highest rarity relic that gives the widest benefit, generally avoiding the color damage unless its a high % and the other wider options are low, anything specific to a girl other then dodge, etc.
I've tried going for all the weaker fights and rejuv/coins I can, I've tried going for the strongest fights I can, the stronger fight paths just end up running out of girls somewhere on the 5th level and the weaker path just gets to the 5th boss and usually walls. I've got 7 wins (though didn't start on hard for 4 or 5 days after it was available) and have used a few more hearts then that but am out of hearts now.
It just feels unfun in general and I'd if I had the option I'd just avoid doing it but the rewards make that not viable.