A pure healer is not deadly, as you surmise the Healing Staff is not really a decent weapon. I for sure can't kill anything with it. However a Healer does not need a Healing Staff. A Templar makes a great healer and can be a DPS Dealing Machine at the same time. Use the Destro Staff for DPS, and the Templar Skills for Healing.
So, roll a Templar, give them a Destro Staff, focus them on Magic, and all your problems and worries are gone.
Once your to L15, the you can add a Healing Staff and start leveling that if you want the more focused healing it can provide.
Thanks and yes I'm a Templar the reason I'm redoing my character is because I was a Imperial Templar now I switch to Breton