Where to start.
If healers could meld other stats onto gear it would be better to bring 3 healers instead of 2. What do you drop for this? If im doing more damage than a DPS class that DPS needs to seriously reconsider thier gameplay choice, if you drop a tank your screwed if adds happen. (remember sometimes you gotta seperate those guys)
If healer = y then big npc that needs to be healed. Not only does this mean every instance would need to be reworked just for 1 role, but it would also be boring. "and so the warrior of light bravely stood behind Raubahn healing him while Raubahn fought the Garlean empire" No thanks.
The raid design comment. While i believe this thread was originally about dungeons, at min ilvl the fights are hard to complete without healer DPS, not impossible.
The Hall of the Novice says to "weave offensive magiks" if no one is dying. You clealy didnt read all of my post, I do this, its a good thing to DPS when you can, it is not however neccesary. The game promoting good gameplay practice, does not mean "omg my healer deeps save the day"
Obviously i prefer a healer that DPSs when they can, most of the ones who dont are the ones doing more casual content, like VA or WC, or dungeons, and its not neccessary there.