Got around 20 of them.
All on my main (paladin) since a while, done a lot of them on 910+ rerolls.
The only one that I've try and wasn't able to get was the blood DK. I've got all other kruul challenges with no issue (around 5 pulls) btw, but the DK is not working for me, even if he is highger ilvl than the others Get 60 try, saw 5 times the P2, get 2 times at 0,6% on kruul. I just didn't get the P1 with this char !
Happy with this system, hope see more of those kind of challenges in the future.