I would strongly advise you to slot no more than 3 enhancements into stamina. The law of diminishing returns introduced with Enhancement Diversification means those last three are having a negligable effect.
However, You could improve your end recovery considerably by adding Accelerate Metabolism into your build (3x recharge, 3x end-mod). Not only is it a great team buff, it's very handy for soloers.
In fact, I'd advise you to take a good long look at your secondary powerset, because it's very, very awesome.
Radiation Infection, Enervating Field and Accelerate Metabolism will all increase the amount of damage you can inflict on the enemy, and keep you MUCH safer as they flail about unable to hit you.
Lingering radiation is a great debuff too. I'd say that it's a good idea to get these all as early as you can.
My opening power on mine is always Radiation Infection, followed by Enervating Field. /Rad leaves no surviviors.
A rad corruptor, whilst capable of healing, isn't really a primary healer, but a debuffer without equal.