It may be worth a double check to see if the Mouth of Hell core can still be rewarded in v1.1.1. After a few hundred kills with no drop, under various conditions, I reverted to a previous version(1.0.8 ), and recieved 2 of them in 3 fights under less than optimal drop conditions.
I got mine in 1.1.1 on my third fight with the King. It does sound like there could be a bug but there must be some other factors causing it.
I’ve done it twice in 1.1.1. (using 2 characters)
First Character got it on the third fight (after around 40 tokens used). Second character got it after almost 200 tokens used (I didn’t count PK fihts… but there was one around every 20 to 30 tokens). So it can take a while…
I’m not sure what caused it to be ome unobtainable for my main file, but I’d burned through roughly 2500 tokens before I did that revert and got it. It;'s mathemetically possible that I simply had bad luck, but it’s not probable, so I felt it was worth a mention. There may be an interfering set of conditions at work here.