Started in Nov 2016. As of right now I am missing 1 girl from Gruntt, 1 from Silvanus and all 3 from Bremen.
I once farmed only Gruntt to get last girl (Miss Spok), I actually reached 1600 fights without a single drop from him.
Then they added those contests and I started doing higher point-worth trolls (Silv and now Brem).
Overall I far passed 3k fights without a single girl dropping, not counting the event ones thou.