Brutes and Masterminds, but I think I played more Brutes. I definitely had more high-level Brutes, an Electric/Invuln and Energy/Energy at 50, a Staff/Dark and SS/WP in the high 30s, and a 20-something Elec/Elec that I was working on. In contrast, I only had one L50 Bots/Storm Mastermind, one Thugs/Traps in the high 30s, and the rest - Mercs/Dark, Ninja/TA, and Necro/Pain - were languishing at low levels. The Necro/Pain didn't get out of the single digits, and I don't think the Ninja/TA did, either.
Dominators were catching up, though, with two - Grav/Elec and Earth/Ice - at 50 (I got the Earth/Ice from 1 to 50 after the announcement was made), a Mind/Psi in the teens or possibly low 20s, and an Elec/Elec in the low teens.