[Osiris]

Ok first you really have to realize how much damage you can handle as a cleric. For me I can handle a fairly good amount of damage so usually I don't worry so much about healing myself and just heal my teammates. I can use some stones on myself if necessary and clerics receive a fair amount of them so you have a pretty good supply. Although it should be the fighter's job to use mock or something to take the enemies from you. Those are the fighters' who actually know how to play. I'd recommend if someone is a squishy teammate as said before heal them and use an invincible on them so you can heal the fighter once or twice before having to go back to the squishy one. From how it sounds the fighter should at least have a pretty good amount of hp/def if they are tanking so should be able to handle a lot of damage and not have to be healed every second. And the hp Regen skill clerics have is good to use on anyone and even in those parties if your fast enough I'd say use it on everyone who is getting hit because it will help out a lot.