Best Trolling ever

You know what my good friends ? The wisp empowering the slamming gorilla in Act 3 was the best trolling ever by GGG. Joke aside, i'm having fun with my Grenade Witchhunter.

I'm actually curious - what does the wisp actually do? I assume the mobs are harder, but I haven't really noticed a difference between wisped and not. Also assuming they boost loot, but not noticing much change yet with that in a2 cruel