the big strength in radiation is on the rad emission side of things. You have two strong debuffs in Radiation Infection and Enervating Field. These two can make just about anything beatable.
On the attack side, almost everything in rad has a defense debuff component. Maybe look into enhancing those as well as damage.
Give it a bit of time. It does work.
Writer of In-Game fiction: Just Completed: My Summer Vacation. My older things are now being archived at Fanfiction.net http://www.fanfiction.net/~jwbullfrog until I come up with a better solution.
radiation infection, ennervating field and lingering radiation should be taken as soon as they are available.
you will see a giant improvement in both damage output and damage taken with those.
rad blast does really well later on, but its a better team set than solo set.
Wait for cosmic burst at 18, that power is awesome
Also, see guide in signature for all your rad/rad needs
Crime of Fashion Level 50 Rad/Rad Corrupter
My Toons
My Rad/Rad Corrupters Guide
Mindscape - Reworking
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radiation infection, ennervating field and lingering radiation should be taken as soon as they are available.
you will see a giant improvement in both damage output and damage taken with those.
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Lingering rad is available at 20, Id take stamina first to pay for the end those toggles use up
Crime of Fashion Level 50 Rad/Rad Corrupter
My Toons
My Rad/Rad Corrupters Guide
Mindscape - Reworking
I'd leave off EF until after stamina. You will ge by just fine withou it till then. Prior to stamina, you won't even make it through a fight before you bottom out of endurace with both EF & RI running.
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If you really want damage, I would consider rerolling a Fire/Rad corruptor instead.
Rad Blast/ will fall below in terms of dmg output (even with expensive sets and procs). The -def debuff is nice, but nothing you need that much considering you will take and use Radiation Infection for every spawn.
There is an interesting topic with all the figures in the same section of the board below, named DPS Fire vs Rad. You may want to read it too to get a clear idea.
Not saying Rad Blast/ is bad. It can be great, and I definitely love the animations and the green clouds of death. But it's not the primary I would choose if I really wanted dmg in the first line.
Good luck 
Rad blast definitely improves on the damage front later on once you get final slots and proc up neutrino bolt(yes neutrino bolt can dish out some real nice damage with 2-3 damage procs 2 nuc's (sho's) and an achilles heel resist debuff proc)
I have a 50 rad/rad fender and a 50 rad/cold corr and i like both alot
So I started up a radiation blast/radiation aura corruptor a few weeks back and reached level 10.
Currently I'm finding my damage output leaves much to be desired (especially compared to my ice/cold corruptor.) Is there some trick I'm missing? I've got the first 4 rad blast powers, radiation aura and AM.) Now, I'm mostly slotted with training enhancements but those should be fine at my level.
Should I be building up accuracy more than damage? Is there some real trick to getting the most out of rad blast or is it one of those top heavy sets?