Saying that, I've not run a 3 Wytch Warcult so let me know if it's OP. My thoughts are you're generally spreading out anyway to get relics but Wych-locking is a pretty cool tactic.
Heh, Not sure when they will hit the table, but like all great minis games, it's just as fun to just carry it around in your head and think up fun builds and lists. :)