Right. I fuzz that on the other end in my game: the distances are calculated accurately, but the monsters are distributed semi-randomly by distance.
The basic process is:
1. Pick a random difficulty for the monster.
2. Pick n random locations for the monster and place it at the farthest one.
n is based on the monster's difficulty so stronger monsters get more chances to end up farther away. This means you can still run into really hard stuff early, it's just less common.
