One way to look at it with regards to a higher ranged skill letting you do more damage is that the more skilled you are the more likely you are to place your shot somewhere more effective thus causing more 'damage', and conversely with a lower skill you are more likely just to graze them and thus cause a minor flesh wound.
Pretty much ^this^. Although tighter spreads are actually less likely to be fatal since you're not taking out multiple organs and such. I remember reading that weapons skill will affect the spread and steadiness of the weapon, but nothing was said about damage itself. I'm kind of hoping it does affect damage since it gives me incentive to put points in my skills. Maxing out your damage is important when DT can greatly reduce the damage dealt.
