There is already a potential problem in this party in that you have a lower-optimisation-level Monk in with a higher-op Wizard. That's a recipe for trouble, unless the Wizard is a shrewd team player. Playing something more powerful and flexible like a Cleric lets you alter to fit the ultimate level of the party a bit. I'd focus on buffs for the Monk and the Ranger to help bring them up to par, whilst still being able to pack some Heals. I'd not do DMM: Persist because that's all about you, but possible DMM: Quicken since that's maybe less powerful but gives you a lot of flexibility (maybe even do something like Heirophant/Innate Spell + Quicken SLA on Heal so you can have a few swift Heals, but DMM: Quicken gives you that option anyway).
Another appropriate option I think would be Bard, or something Bard-like. Again, skill-monkey with some healing, but it's mainly about support. You have a couple of martials (Monk, Ranger) who probably need some help, so by buffing them (whether with Cleric buffs or bardic music or whatever) you help level out the party a little whilst still being able to contribute yourself with your wider range of abilities (skills, utility spells, etc).