For right now, I'm going to say Dark Knight.

I'll really need to see all three in action, but Machinist isn't dual wield and I do already have a DPS role mained, so wouldn't be a bad idea for me to level up a tank or healer.

Astrologist, I'm just not sure if I like the Orb part of their weapon. The deck of cards is a great idea though Which is why Dark Knight gets the vote for this poll.