James, no it will not hit. They can tech roll out. The only way to get a guaranteed GP is on a solid knock down where they can't roll.
As far as spammers go, dash block (wave dash) up to them and block the clones. If you block it close enough you can counter with a dash punch on his recovery. same thing goes for Lu Kang. You can't punish his lower fireball but you can come in and apply pressure on him.
That loop combo works like a charm. I have done it several times in a tournament
It's freakin nice. I have my own little version of it but it is mainly the same.
Here is a nice 50% combo mid screen. F.4 DU.4 EX.GP x3. shit works nice cause they can't roll out of a hard down
To punish people that have rolls after block, like Scorpion/Meleena/Smoke, I use GP Jumping Neutral Punch back 1,2,4 dash punch. Shit is easy and does good damage without the difficulty of some of the other ones out there.
Hope that helps.