I don't like how they changed healing to be based on RES instead of INT in Disgaea 2 onwards. It makes sense in the context of giving people exp based on how much they heal people to encourage specialized healers (but even then it's still exploitable) but I miss teaching my healers offensive spells and using them as mage/healer hybrids to both nuke enemies and heal allies with high staff mastery and INT. It was a very practical application of the mentor system.