Take materia of everybody except Aeris and only give her Bahumut and the restore-all materia combo, put everyone in the back row, using Bahumut is a good strategy and when the demon wall uses avalanche I guarantee that everyones Limit breaks will go up provided they don`t die, so just use those as much as possible, by the way what limit breaks have you got for each character? and maybe it wouldn`t be a good idea to use vincent`s limit break because then he can`t revive anyone.