This variant posted under WoA - "Adding Surprise Check" and the resulting discussion therein gave me a very simple idea on how to make movement of heroes and the subsequent exploration more interesting without adding more dice rolls to the game.
Basic "Guard" variant: If a hero explores and is attacked by a new monster spawned on the just revealed tile, each unused point of movement adds +1 to the hero's AC. This simulates the hero having more time for observation and setting himself on guard.
If the hero did a double-move, each movement point used in the 2nd action makes the hero suffer -1 to his/her AC instead.
Advanced "Guard" variant: The AC bonus granted must subtract the monster's level to a minimum of 0. So a hero with 2 unused movement points that encounters a 3XP Wraith would get no AC bonus (2-3=-1).
1. The AC bonus is only for the very first attack by the monster.
2. The AC bonus does not apply to event-attacks and traps in the encounter deck.
3. Being Slowed and Immobilized means the hero has 2 and 0 movement points respectively. Choosing not to move when Dazed also means the hero has 0 movement points.
4. If the newly revealed monster's first attack is against another hero (not the hero that explored), that hero does not get an AC bonus.
5. If the monster's attack is an area attack, only the exploring hero benefits from any AC bonus.