Um... I don't know where YOU'VE been, but I see those two powersets a LOT.
I'd go with Zombie Summoning for Masterminds. I hardly ever see those any more. 
Of course, this changes between each server, and who knows, maybe other people have seen lots of Zombie MMs? Ah well, whatever.
I think he meant for Corruptors. It's probably Rad Blast.
I really don't see many elecs or darks.
I say probably Energy Blast.
I've seen quite a few Dark Blast and Assault Rifle.
What's left is to normalize all Assassin Strikes and improve Stalker's old sets (Claw, MA and EM)! You don't need to bring back the missing PbAoE attack. You just need to make the existing ones better! For example, make Slice a WIDER and LONGER cone.
Rad and Energy are the ones I see the least, with AR very close.
I wouldn't say rad blast is least played since you can fill it full of awesome procs.
My vote for least played is NRG blast. NRG blast on Blasters and Doms is good. NRG blast on Corrs is subpar. 2nd least played in my book is Dark Blast.
I don't see Dark Blast or AR very much.
I see EB paired with Kin a lot... and Rad is often paired with the other Rad.
energy, because it sucks and is pink.
Don't sugar coat it. Tell us how you really feel. 
fire blast
AR? EB?