2, warrior and necro.
I have all others but I play them very rarely.
I have all 9 but dislike playing thief, ele, and revenant. Something about them really doesn't work for me. Maybe leveling them has sucked more than other classes?
I have 6: necro, ranger, warrior, revenant, guardian, and elementalist, but only play 3. Necro/minion master, ranger pet/archer, and been messing around with a warrior. He is new and kind of longbow/axe & shield... not sure about him yet.