I only did ffa kk on the first day and now I have no friends to ffa with so I cs, and based on cs kills I seem to get a drop at least every 45-50 kills. Need to start logging though.
Cba to open it up atm but out of the 1.6k kills it came to something like 1/39.
When looking at where RoW was used it dropped to around 1/36 and when we were CSing it was at around 1/40. I did more CS than FFA so that would explain why the overall is closer to the 1/40 rate.
Good topic about it here:
http://www.xp-waste.com/kalphite-king-drop-log-t3603.html
Our combined logs bring it to 1/39.8125 which is 64 drops in 2,548 kills.