Quote Originally Posted by 'ElectronDF',index.php?page=Thread&postID=151104#p ost151104
You can't target based on raid symbols, you can't perform actions based on raid symbols. They are just there for your visual benefit, not for WOW's use.
Yes of course, the raid symbols help as you know whether or not the mob targeted was the correct one or not due the raid symbol attached to it (or lack of).

I've added some large red text stating "target by name" to the first post. It's not much, but if you actually read the wall of text you come to understand how it works.