Sometimes to get the gain level you want, there is a lot of noise along with it. Ain't nothing wrong with that. And there ain't nothing wrong with using a noise suppressor, either, if that gets rid of the problem!
When you put OD in front of an amp, you are going to get noise, since you are magnifying your guitar signal 3x (OD > preamp > poweramp). If you find the hiss unbearable, then yes -- a noise suppressor will help.
A noise suppressor will also help eliminate feedback at high volum levels.