The Halfling
Explorer
I think if it was released now, they'd likely have made Runepriest a build for clerics (bsaically replacing the also-not supported Str. Cleric), and Seeker a Ranger Build (which they essentially did with Hunter). Psionics... yeah not sure about them.
I can see that given that Essentials seems to be trying to winnow down the total number of "base" classes, and upping the number of sub-classes, like 2E did in a way.
Given the fluff of the class though, I wish that the runepriest was a leader build for the invoker rather than the cleric. A cloth wearing leader would be something currently not in the game, and wouldn't step on the cleric toes.
The Seeker I definately agree is the Hunter with Primal as the primary and Martial as the secondary.