Int thus determines Mana pool size, while Cha determines Regained/period.
you also cant just fix it with Manacost=Spell Level. Look back at TBC WoW, Paladins were the prefered healers because they had a heal several magnitudes more effective for it's manacost which also happened to cost less per point of healing then anything Priests and Shamans got. Druids were still healers because they had regeneration/rejuvination heal over time spells which Priests and Shamans didnt get.
@ Wombat: A Magic System as devised by Jack Vance. Magic is all ritualistic, but the rituals have last second savestates that allow them to be saved for later.