A suggestion for a new Sona W?

Uh well, I guess some of you people saw my suggestion how to make Sonas rework "more" powerful, though my suggestions were actually really op (check them here if you really want to) Probably adding magic resist to her Heal/Aura might be too strong for some people, so I guess we should really think again how to buff her W without making it that overpowered.

So, how about we do this: Instead of a scaling heal, based on missing health with an flat shield, how about an flat heal with an scaling shield, based on missing health? It's strenght and duration is increased for each 1% health missing on the target to a maximum of 200% of the shield. It's just a small idea, but in my opinion, it will make it more worth for a Sona player to tag her low health allies with it, so they benifit more of the shield than higher health targets. Not to forget that the shield will also will fade off, so her stalling power won't the be that high as well.

It's just an idea, and I think some people won't agree with it, but it's probably better than Sonas current W in my opinion.