Well obviously you're powerleveling the build so that means you've skipped over a lot of your own experimenting and learning how to play your character. I'd strongly suggest you solo it some or play with friends so that you get an idea of what your powers are and what they do. I don't mind helping out low-level players, but when I run things at 50 it can be irksome to have to explain to someone what their powers do and when to use them. I think I can safely speak for many players when I say that I mentor on my low-level guys and when I am on my 50s I don't want to babysit.
That out of the way, I would suggest you download Mids Hero Designer and post a build for critique so that we can see where you might be going wrong and correct you. Since you haven't had experience with your build, you could easily have problems that you don't know to tell us about and that we wouldn't foresee. We can't just tell you every in and out of playing the character - firstly, that would be prohibitively comprehensive, and secondly, it would be tailored to the playstyle and preferences of whomever wrote it - which is not necessarily the best way for you or anyone else to play it. Generally speaking there isn't one and only one right way or best build for most anything in City of Heroes.
As for "why its a good idea", Radiation Emission is a very powerful debuffing primary and can be a key player in major battles against Archvillains (AVs) and Giant Monsters. Having a well-built and well-played Rad will make you an asset to many teams. The key Radiation Emission powers here are Radiation Infection, Enervating Field and Lingering Radiation. DO NOT SKIP THESE POWERS.
As for Dual Pistols, one of its main strengths is the ability to change damage output types using Swap Ammo, something no other blast set can do, so you can tailor your damage output type and secondary effects to what you are fighting. Keep in mind that if you do not have one of the three special types of ammo on then your secondary effect will default to knockback, which can make some melee types unhappy if used poorly.
If you have any specific questions, feel free to come back and ask 'em.
Iscariot's Guide to the Tri-Form Warshade, version 2.1
I'm sorry that math > your paranoid delusions, but them's the breaks -- Nethergoat
P.E.R.C. Rep for Liberty server
Okay So I Made a Rad/DP Fender I like Him So Far Hes Leveling Very Fast Wink Wink.
Currently 39 , And I Wanna Know What Am I To Expect Out Of This Build? I made It For Fun , Alot Of People Say Its a Good Idea But Never Explain. If Someone Has a Build that Could Share I'd love to see it 
But Still Need to Talk to Someone About it 