An easy trick discovered while trying to test various [mostly wrong] guide tips on pulling Jarel's sword from the stone (see that thread - XP turns out not to matter, you just need 62+ total STR):

The trick is quite simple: attacking monsters will turn with you (except when you face a wall). So, engage the group, then turn back the way you came: the monster will appear in front of you, and you can back up or strafe through where it used to be. Monsters have a pretty limited range beyond which they do not travel, so keep going until the monster stops.

This mainly helps with patrols in cities, which respawn whenever you load. (The respawning helps when it reduces a group of 3 to 1, but it can really be a problem if you're trying to not gain XP (which turns out to be useless, see above!)).

(The limited range also allows you to abuse arrows and spells by firing at them from one step beyond their range. If they stop just in front of a corner, you can see and fire at some but not all members of the group by facing the adjacent wall or sometimes the corner itself, and at least thin them out. Remember that loading respawns monsters though - so if you save after maneuvering enemies, you'll have to re-attract them if you load!)