Yous gots to fill me in with this trick xD
Anyway, yes, they wont detect you cheated. It'll detect how quick you done a mission and flag it as
Abnormal completion or something. It is recommended they could have your account flagged aswell. So I'd do this in a party with friends or something.
TL;DR?
It'll detect how quick you've done the mission and calculate your damages you delt. So it wont (or may) give you rewards.
If I were you, I'd just make bosses have lowered health. Less chance of being banned or flagged.
List of things I remember they keep track of
Damage Taken (by Mobs)
Damages Delt (To Mobs)
Attacks Taken (From Mobs)
Attacks Given (To Mobs)
Time mission start
Time mission end
That's all I remember.