I have now managed to complete the battle. For the benefit of anyone who ends up in the same position I was in I am writing this comment on how i managed the fight despite only having 2 pins that worked.
Simon already had the Givini Pin. He kept it.
Carina was getting perma stunned, but Aka had not due to the Heirloom pin. So I gave Carina that pin instead.
I then replaced Aka with Robin. though she never got to cast a single spell as both Simon and Carina were slower with their cleanses than Lilith. they would cure her, then Lilith would reapply at the start of the next round. However keeping her healed meant that some of Mestans attacks went to her drawing them away form the others that were not stunned.
Having Carina able to act meant that Simon could stop healing and start spamming incubus strike, allowing me to do more than just stay alive.
finally, I added Nalili, because her tormented shield performed as well as a the 2 pins. yes she still got the occasional sexbind, but that was maybe once every 4 turns, so I could work around that. (additionally other characters can use the tormented shield if you really dont want to use Nalili. Nalili also had the benefit as she is half physical, so when her sex skills are restrained by sexbind, she can still be quite effective with basic attacks for that round (thus no lost rounds, just slightly less effective ones, and one round of basic attack is more lust for the next round too))
So basically:
Simon: Aggressive incubus strike with Givini Pin (or another if you don't have but have one that i didn't have), using support allies only if Carina gets overwhelmed and needs a little extra help for a round.
Robin (or maybe Hilstara as she will have more health): wont be able to act, but is a valid target for enemy abilities, keep the other 3 getting targeted as much. so still heal her. (you could give Simon the shield and then have a pin for her if you want, i suspect that would work too)
Nalili: pure damage, just keep hitting. The shield will let you do it. (unless above alternate idea was used, and Simon had the shield instead, one of your 4 will be stun locked, its either this or above)
Carina: Heal if any are low health, cleanse if Nalili gets sexbind, you can try to cleanse the other, but it will be pointless. Carina must have the Heirloom pin (or whichever of the major pins you have).
If you only have tormented shield and 1 pin, I can see this potentially working with Nalili + Qum or maybe Nalili + Yarra/Riala. as long as the second in either of those combos has the pin AND has enough defense to never be one shot and spam life steal abilities to stay full health.
I'm glad to know that there are in fact alternative ways to win this that don't involve starting from the beginning. I hope this helps the next person that finds themselves in the position I was in.
Edit: Tested the Qum combo i started above, doesnt work with my pins (Givini and Heirloom, as Qum cannot equip them, so would only work if the pins i dont have might work with Qum, so Carina is likely not negotiable with limited pin availability)