I've been able to consistently beat insane with the following at 7723HP:
Healer/Achilles Leads
6* Harpy
5* Cerberus
5* Cerberus
6* Medusa
Low HP but the 3 attackers can kill a Satyr in round 5 easy. The 5* Cerberus skill leaves just enough HP for you to recharge the last Satyr in any round at 5 lines, then switch to max lines to kill them off, leaving you with all 3 attackers ready for the next round. I'm using Medusa cuz that's all I have that makes up for the low HP.
Only trouble is getting past round 1 without the attackers charged. I've been able to get enough hearts to keep me going til I kill a fairy. Once that first fairy is killed, you're guaranteed to pass it all unless you screw up. Or by some freak of nature your entire board ends up green or blue and you kill the last Satyr too early. Kinda hard to do at 5 lines though.
I hope this helps the players who don't have real good cards. All cards I used are pretty basic easy to get cards (besides Harpy, but you can use any maxed HP card for that HP boost).
EDIT: My luck ran out. My last go, I couldn't get hearts on round 1 for the life of me and ended up having to revive twice before killing a fairy.