Back in the old days - before 10sec spam pots / teardrops and what not else - it was fun to cast pet prevent on near dead targets along with toxic pot and watch them falter when their molly didn't heal and they couldn't use pots.
Oh, the joy.

It also sucked if I was the guardian on whom it was being used on. That was before I discovered the use of Blue Drain I simply love that skill, trolling reasons included.