The original download version release (1.004a) switched all the weapon expertise skills to a percentage damage bonus, rather than having some with fixed amounts. Apparently the 1.005a update reverted back to the way they were in the disk version of the game.
For the bow, the True Shot skill should give a damage bonus; the expertise skill just helps with recuperation time. True Shot, and the damage portion of Crossbow Expertise, were broke in the disk version of the game, but fixed in the original download version. With some other expertise skills reverting to fixed damage boosts in the 1.005a update, though, I don't know if I'd put too many points into True Shot without testing it, though (I can probably check that later tonight).
Even without True Shot, though, archery is very effective (especially combined with Poison Weapon).
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