That's called your opinion (and a logical fallacy), not logic:P. I agree that lightwell is harder to get optimal use of from the raid than barrier, but apart from placement it's not a responsibility that the priest is forced to shoulder, I also doubt that holy is designed/balanced around the raid making perfect usage of the lightwell (more likely around lightspring). That you gear for as much mana as you need to do your job, and not beyond that, is completely standard and a widely accepted premiss as a healer. The net result of a spec having less regen is (unless it's a difference that can't be compensated by gearing, and in this case it isn't, at least in 10 man) a difference in how much output you can gear for.Because you are arguing against a brick wall of logic. Holy mana is worse than disc. Lightwell is the hardest healing cooldown to achieve optimal use from, unlike any other.
You are arguing to hear yourself speak. Or read what you write. Or [insert appropriate metaphor].