Don't do it, unless you are either captain uber player or just like to get your butt kicked all day long. My Merc was my main toon and my first to reach 50. Pre-50 was a lot more fun. After 50, PVP is usually less fun than banging your head against a brick wall.
My assassin, marauder, or sniper - all are still fun and I can usually place in the top 3 in most Warzones. On my BH I am almost always dead last on my team. I have tried all three trees (pyro seems to be the only one remotely worth it).
I do not have fun playing BH anymore and will prob not be logging him much at all until there are MAJOR improvements.
IMHO don't even bother with it unless u want to have a another toon to craft with or just like to punish yourself...