The arrogance of some people

[RiceisNice]

less chances to make mistakes: Some people in this thread have been advocating that healers are best when they're pushing the edge, getting in every possible point of damage they can manage, skirting the edge of letting players die without quite going over that line. That approach is creating more chances for serious mistakes, not less.
(Note: This last argument applies only to the drive to maximize healer DPS, not the one about wanting healers to do a bit of DPS in downtime when they'd otherwise be idle. I don't really have any problem with the later.)

Just to chime in on this , incoming damage to a tank can get very, very predictable, especially when it corelates to the tank's (lack) of tanking stance or cooldown utilization. Best example I can come up with is SMA's bee boss where you don't really need to top them off after. Every bit of damage down to the auto attack and "mini-tank buster" comes at a predictable interval; best example I can come up with is SMA's bosses where I practically do not need a heal on my warrior up until after the first breath sweep, or the bee boss after it's first mini-tank buster.

less mechanics to do: The mechanics are the fun part. It's boring to just burn through every boss the same way. Plus there's the fact that many of the dungeons whose mechanics are now routinely skipped are low level learning dungeons designed for teaching new players how mechanics work. The biggest reason why so many players end up in endgame (or at least late game) dungeons totally clueless about how to handle mechanics is because the simple version of those mechanics are too often skipped in the earlier dungeons that are supposed to be teaching them.

Semantics, but realistically speaking a lot of bosses don't have that many engaging mechanics to begin with, even in context of new expert dungeons that players have already queued for. Granted it's a bigger underlying problem (the dungeon in general being undertuned relative to the level sync, or when a typical player can access it), but you can't honest-to-goodness say that a lot of the low level dungeons have "interesting" mechanics even if you were to take away the overkilling of it, and it really doesn't punish the players enough to the point that they can fail every mechanic and still get a pass. Aside from that, the "simple version" mechanics are ones that are reoccuring throughout the game, not specifically to the boss fights (telegraphed AoEs for example); I wouldn't go as far to say that it's the reason why players fail in endgame dungeons because they're clueless on mechanics.