The only issue with that happy plan is that you get 2 HPIP for every point of mdam. So you might want to rethink that. You definitely do want to +16 your wand/staff, and you do want to calculate that in when you look at mdam bonuses on gear.
Mind you, some people like to clean tier weapons with stats- and healer is about the only class that can get away with that on a mainhand, but you still need to plus or you'll be gimping yourself badly.
Knights also do it :p
But on topic: Yes, you need to plus it. Plussing weapons gives a TON of magic damage, which affects heals quite a bit.
Oh, and you're a p/k.. don't use a staff. Use a wand and a shield.