The one thing I've generally disliked about playing thieves is that their backstabbing ability rarely comes into play when playing without a grid. It's a shame, too, as it is a cool ability and the whole idea of putting a thief in the thick of combat is just plain fun. Well, dangerous too, but danger is fun. :)
With the grid you can show placement and facing and the thief can move into a backstabbing position right in the middle of combat. When playing gridles, or Theatre of the Mind, those opportunities are pretty much lost. Let's try to work them back in.
Surprise. When the thief gets the drop on an opponent you probably should allow the thief to make a backstab attack. He's going for vitals, the opponent has his guard down, it should have the potential to be very painful.
Initiative on the first round of combat. This depends on how combat heavy a campaign is that you are running. If you want to make the thieves more than trap monkeys in your campaign, give them the opportunity for a reduced backstab if the thief beats their opponent's initiative in the first round of combat in an encounter: + 2 hit instead of + 4, and one multiple less on the damage bonus (so the damage bonus wouldn't kick into level 5, where it would be at x2 and move up from there). Of course, this also puts the lightly armored thief in the party's front lines.
Pick Pockets Skill - if you treat picking pockets as more of a distraction type skill, one thief could set up a target for another thief in the midst of combat. Would work very well in a dark alley ;)
Remember, what's good for the goose is also good for the gander. If you put any of these houserules in play for the PC thieves you've also made the NPC thieves more dangerous. That can only be a good thing, right?
[Friday Faction] The Elusive Shift - It is commonly agreed that Dungeons & Dragons, published in 1974 by TSR, Inc. was the first roleplaying game, but was it? If not, what then was *Dungeons ...
51 minutes ago