I was on the receiving end of the Kindly Ones in an MP game with friends at work, playing as Ogre Kingdoms. I was already on the ropes. That alone wasn't the KO, but it certainly sped the process. I would say it was definitely a worthwhile move by my opponent.
I have experience casting Wild Hunt in a game on this forum, my first such game actually. In whatever version of CBM we were using it was like level 4 or 5 Conjuration. I was playing Fomoria and rushing Conjuration to get Morrigans and cast it around level 20. I then couldn't figure out why no one would respond to my requests for diplomacy.
It was a small game, 6 players on Tyrande_2. Casting it so early in such a small game made it much more effective. It was actually the only forum game I've won.