Honestly, you don't want to hear our advice. Your DM needs to take 4 characters from the Sultan's of Smackdown and wipe the floor with you. Turn about IS fair play.
The other option is to realize that the Prestige Class is unbalanced and rework it some. Like drop the spontaneous casting how it is and maybe you can spontaneous cast one spell from your domains per level as stated above.
Also, about the figter VS you...he's suppose to woop but in combat that is what his job is. You are a spell slinger and healer, and should be good at that. I don't see why the rest of your party just doesn't mimick your character and tactics...
Gariig
The other option is to realize that the Prestige Class is unbalanced and rework it some. Like drop the spontaneous casting how it is and maybe you can spontaneous cast one spell from your domains per level as stated above.
Also, about the figter VS you...he's suppose to woop but in combat that is what his job is. You are a spell slinger and healer, and should be good at that. I don't see why the rest of your party just doesn't mimick your character and tactics...
Gariig