It *is* possible to be a Healer and still do decent damage. If you focus on using only Staves, max out MND as quickly as possible, and pick up some good Staff Skill Force Mags (and switch to Staff Affinity later on once your Affinity cap raises), then you can technically pull off the Healer role, it's just very tricky. Staves aren't the strongest weapons around, so your DPS will be lacking compared to say: Twin Swords. They also have limited ranging capabilities (and their ranged attacks are quite weak) so some bosses (like Beelzebub from my own experience) will be pretty tough to take down. That being said, Soul Strike VII is pretty badass, and the healing/buffing skills can be literal lifesavers. *If* you decide to create a pure Staff user some time in the future, I'd recommend upping their durability to around 4k. Some Staff skills (like Soul Strike) will devour your weapon's durability. Also, once MND has been maxed out, add some points to POW. I've read that POW increases attack speed a little, which with Staves is something you want (as well as the Swift Combo Card).
I can't give any more advice about Wands, since everything I can think of has already been said. Unfortunately, due to the way Onigiri has been made: Glass Cannon Mode is the only viable strategy since defence is meaningless, and there's no actual armour items. It's a case of max out DPS, learn to Just Guard, learn to roll whenever you're unable to Just Guard, and try to minimize Ping as much as possible.
TL;DR Healer *is* possible if you Glass Cannon, but there are better builds. Glass Cannon is the only strategy.