I think your medica II proc suggestion is too overkill with how good it would be, assuming I understood you correctly. (Ie. 16% per tick for 8-mans, effecting every single tick for the on-going 15 secs).

Cure III, in my ideal world, would have a visible cast-area to it, kind of like Shadow Flare has right now, but with whatever they decided to put the radius to, so you could actually place it as opposed to eyeing the range of the spell, sort of, which you have to do while keeping server lag and player movement in mind. It would also be nice if we could have less reliance on procs - especially procs that are generated from casting cure II, because ideally we never spam cure II, thus activating the cure III proc from cure II means that something is not going too well to begin with, apart from certain situations. Would be nice if we could have both cure II and cure III procs activate from our cure I - while only being able to use one proc before the effect disappears.