Ghostcrawler on mana management
We do want mana management to be a part of the game. The right way to play, especially for healers, is not to spam all your heals as fast as you can and then go out of mana. Instead, we want to reward players who can rely on hots, limit overhealing, coordinate with other healers so they aren't double healing the same target, and knowing when a fight is won so you can take a break and start mana regeneration. If healers don't ever go OOM, then the only way to ever lose a fight is for the bosses to hit so hard that sometimes you just get bad luck, to have strict enrage timers so you have to learn to maximize your dps, or make the fights so complicated that they take a lot of explanation and practice. In the good old days, one of the best gear checks was could you keep the tank (and to a lesser extent the group) up without going out of mana. (src)