There isn't a single answer to the healing requirement problem because there is so much that contributes to it. You can boil it all down to a lack of foresight from the dev team. As an example, this nearly all SMN run I heard about could be eliminated if they make Everlasting Flight so that the regen effect doesn't stack. To me, an issue like this is a glaring one that should have popped up during testing. Even if that is not the case, a lot of changes they make is a result of a design flaw that is exploited by the playerbase. Like electricity, players will find the path of least resistance.

No matter what they do to healing, players will track down the methods of how to get things done using the least amount of it as possible. It's just such a shame that this role gets stepped on during a player's path to greater power. We are needed the greatest when content is released, and the first to be outed as players obtain the better gear.