Imagine you have a friend. This isn't any normal friend, but a friend that you really, really, really want to get interested in World of Warcraft. To this end, you have the brilliant plan that if you let him raid on your character, he'll be so taken by the experience that he'll be level 85 within a week.
Naturally, this goes badly. Recount shows your character below the tanks every attempt, as your friend spends half the fight attacking the wrong target and the other half of the fight attacking nothing at all. Of course, that's only on the fights where he manages to stay alive, which is one in 10 attempts.
Now, imagine that in order to do your maximum DPS, you have to let that friend raid with you every single fight. If you choose not to allow that friend to raid, you'll lose about 3,000 potential DPS. However, if you choose to let him raid, you run the risk of his dying, attacking the wrong target, or standing in the center of the room while he mentally alt-tabs.
Welcome to playing an elemental shaman.