Lost a tourney once failing a stupidity test on my ogre tyrant with a re-roll. (mawseeker and jade lion, thats 9 with a re-roll)
Only happened once in 8 games but it was the last game and lost me the match and thus the tourney.
The only time i have ever lost points on a Daemon Prince ever is when he broke from combat in the last turn of the game with the bsb in range (thus a re-roll). Lost that match too. (500+ points broken at the end of the game + general, sigh)
My point is that if something can happen it will happen sometime and that time may very well cost you a match. dapredator66 is correct in saying that the chance of seeing a terror causer in 1k points is low, if you want to guarantee you will pass the test take slaanesh.
A rhetoric question. I have no clear answer for you but they clearly are stronger or at least equal to any other cavalry.are fully upgraded knights of chaos the best cavalry in warhammer?