Think of them as similar to the Assassin's Trap skills. You put 'em down, watch them do their work, then re-cast them as needed.
They? Hehe, the whole things been done exclusively by one guy, a very obsessive German/Genius (I do mean actual Genius, he's doing like five extremely difficult courses on real mind-bending subjects AND doing Median at the same time) by the name of Lazbro.
Also this: A list of builds. NOTE : Some may be outdated due to subsequent patches after the one the guide would have been written for.
I also believe that a new version is coming out within the next few weeks, so don't feel too bad if you find a character you make now becomes nerfed to buggery come the patch.