Like Parog said.. i always "played as if I had a GM watching":
- I never clear a map from all cests, because a normal user can miss a lot of them. Sometimes i skip mobs too.
- When i farm Arcanists, i always open any other strongbox...no picky, to give them reasons to doubt me of cheating.
- If i want a specific master, i do other masters in between to clear any suspicions.
So, even if i use the hud, i don't use it blindly

.
And all this leads me to the conclusion that they banned most likely for user behavior by using the hud.