So, I just found out that with B4, the heal spell comes in a strategic and tactical variety.
IMO, it's really not necessary, and is easily exploited. If a unit or two needs to be healed in-between tough battles or monsters, and you only have the tactical heal spell, just pick a fight with a weak enemy monster and dance around them while casting the needed heal spells, and then just finish them off when you're ready.
Maybe just increase the manna cost for a heal spell instead of turning it into two.