Help with rad/ninjitsu attack chain?

['Tan]

I've been wanting to try a 'different' combo lately and am enjoying how my new rad/nin is playing (currenty lvl 35). The defense is impressive and rad has impressive ST/AoE damage.
However, I don't think I'm utilizing the ATOs and bonuses from ninjitsu to their full capabilities. There seems to be a bit of strategy involved with this combo since you get the crit bonus when you're 'hidden'.

If you're coming up to a new mob while hidden, does it even make sense to have irrad. ground on? Or should you hit Atom Smasher out of 'hide' and then turn irrad. ground on followed by the ST attacks?

Also, what is the best power to slot the 50% crit proc ATO in? I was debating between the t1 attack or proton sweep.