i would say there is no best complimentary skill to cow, and if there is, it is likely to change, and then change again (seeing as we are in early development).
my advice would be to pick what you like from a role-playing or game-play perspective (if you want some healing and support, go druid - defense, go unarmed...etc), because if you go for the "most powerful" build you're just going to get pissed when it gets nerfed, and you are playing a build you dont necessarily like aethestically and now you lost your power too.
