Just a little clarification - I *do* use missile weapons as much as possible. But sometimes the party gets swamped, and all-out melee is inevitable. Except for the mage, everyone else has a decent melee capability. That's when the thief comes in. Can't hide in shadows while in enemy's view; can't afford invisibility potions to drink on a regular basis. Hence backstab's of not much use.
Sneak attack OTOH doesn't require the NPC to be invisible/hidden. Just stand to the side or rear and WHAMMO! heavy damage.
The downside is that it only works once per monster.
