There's only a few tips I can think of that might help you:

1) Adding to DPS is slow and mana costly, so you may have to really think about where and when you want to do it
2) Abuse Esuna and don't heal DPS right away
3) Talk to your party! Get one of them to help with ghetto cures when you start to struggle on certain fights. After DPS gets Esuna'd...let your help top these guys off
4) If no one wants to help you, try anyway. You never know just how much you've learned since last attempt.
5) Reattempting fights only works as long as somone is learning something...sometimes it's best to just walk away if nothing is working.
6) Overhealing is a mana sink & healing generates hate regardless how much of it gets used, so only do it when your party gets the biggest benefit.
7) Free cures are just that. Only pass these up when the hate gained outweighs the benefit of a manaless cure.