Ofc you arent supposed to use the dreamspitter on every mob you see.
Ie. the water ellies in red fens seem to have massive amount of hp so its better to use Tomb of Jade and then drain all their lvls. My team members were wondering why it looked like the ellie GAINED health while every1 else was beating it with normal weapons (I tombed + dreamspitted it).
They didnt notice I was using dreamspitter until I said so... And then the other stunner monk started to use the tomb too :P
EDIT: To see the difference, try to solo the 1st mob in epic Claw of Vulkoor with only stuns, and then try with stun + dreamspitter.