These discussions tend to overlook the other half of the party. If the dps don't or can't burst down a big pull, you're risking a wipe for little to no gain.

But if your damage is up to scratch it's really a no-brainer. A dungeon is basically no more than a set amount of damage the party needs to deal. Even with potency fall-off, dps increases with the number of mobs in the pull so the more you pull (without wiping obviously) the better. You lose some of the healer's damage output, but there won't be many scenarios where that outweighs the extra damage done by 2 dps and the tank.