1. Is using scroll for shooting cheating? No, it is not.
2. Should it be dealt with? If it is a major problem, then yes.
3. Is it a major problem? No, because it gives pros and cons.
I've tried scroll wheeling before and practiced with it. It's very effective once you're able to aim with maximum fire rate.
IMO, even if they did remove the possibility to change the keybind of "Fire/Shoot" to either "Scroll up/down" then I would not really care. Although, I can see your point with that there is no "learning curve" to it. Learning the fire rate of each weapon can take time and skill.