The only defender I could play consistently enough to get to level 50 in the old days was RAD/RAD. Sure the blast set was underwhelming, but Radiation Emission was simply amazing. Especially since EMP pulse hadn't been nerfed. You could hit AIM, then iridate, then EMP Pulse, go make a sandwich, grab a beer, and mobs would still be held when you got back to your PC and fired off Atomic Blast. And even after the Nerf that defender was easily one of my favorite toons. Heck I might just build him again so I can see what a monster he'd be with IO sets and incarnate powers. Not to mention insta snipe, and a crashless nuke.