Adding more to the point: there will always be some subset of players who just won't improve no matter what changes you do to the role. There's no point in making those healers 'heal better' because their next likely course of action is to quit the role instead of improving, something that's seen as a cardinal sin to the eyes of the job devs.
Coincidentally, these are also usually the same subset of players who don't even touch their dry, barebone today's dps spells. What makes you think having more of them suddenly mean they will start paying attention to these and forget about healing? The answer? They won't. They're already shaking to even press the proper healing button and you want to make lives harder for them?