Any time you are breaking the EULA, you are at risk of getting banned.
Its alot less risky inside of an instance, with other people who are also breaking the rules, but the chance is still there.
Just like if you were smoking crack at the mall, you would probably get arrested.
Smoke crack inside a dope house? Probably wont get arrested, but youre still breaking the law, and the chance is still there!
So, in my opinion, you are alot better off cheating inside a dungeon, that way other people who dont cheat cant see you.