Yeah..I will tell you from experience lk does nothing at all. I comped one item to test, with 1k+ lk I got a minimum comp on DA. Then i tried with 200 lk exactly and got a +15.. So really it's all real life luck, I just comp with whatever i'm wearing now.
Also, the compound mastery skill for foxes does absolutely nothing..Just a warning to anyone who was going to get it..I almost think I comp lower with it than i do without it..