Yeah. Night, for example, doesn't believe that you get a lot of experience for deceiving monsters.
1. The hero has units in his army (a thief is an exception for level 1 monsters) or a hero without the "stealth" skill of the corresponding level.
2. The monster is fighting under some flag.
3. Experience is not awarded for deceiving the hero.
P.S. What I wrote is probably known to everyone. But just in case...