Excelsior

I may be missing the obvious, but what does one have to do to get credit on their achievements for killing a Champion? I have participated in 4 so far and still no credit.

I have received power scrolls for each one and even a skull at one.

I kinda assumed solo champ kills, but haven't actually checked myself nor asked anyone who has solo'd a champ.

I have a solo kill and that is noted in my ach as well as 12 champ kills, so it does record them. I think I have been involved in more than 12 champ kills so perhaps there is some formula associated with group kills
Michi