Originally posted by Suzaku:

So kill the shaman. They die in 2 hits. Or focus the troll. A single heal is worth roughly a single hit. DPS through it.

Or don't. If this is enough to make you rage, you won't last 10 seconds in the swamps.

Wait until they run into deathsquitos on the plains. Or any of a number of enemies later on that are going to ruin their night.