I found this by pure luck when fighting the shadow of Diablo on my monk.
At 100%, ~66%, and ~33% the shadow spawns a clone of you.
However if you use Seven Sided Strike just before he spawns a clone of you, there will not be anyone to target or clone so you can just go back to fighting the shadow.
This also works in Co-op games, the shadow will not clone you but will clone others. So there will be 1 less clone to fight.
Not sure if this will work with any other spell for any other class... but go ahead and try with any spell that makes you untargetable.