Depends on fight. On most fights there is a limited amount of dmg you can do on adds, so picking talent that maximize overall dps may not always be the most optimal thing to do, better to have a discussion with the raid and come to a conclusion of how much overall dps is needed on the adds and wich classes have mechanics that most effectivly can deal with that without losing singletarget dps on boss (since this is usually the most important).
For example, and aoebased spec with less singletarget dps is sually not the most optimal spec on a bossfight like misstress.
Your question seems abit to simplistic thou. Its akin to asking "Is the football player that scores the most goals the best player in the world? and should all football players strive to play like him?"
The obvious answer here is no, football is a sport that require teamwork, its the same with raiding, the most optimal way to play a fight is to thunk as a team and not as an induvidual. To utilize the teams combined abilities and in the most efficient way possible divide those abilities to defeat the encounter.