Topic shamelessly stolen from official forums.
So, obviously, pistol/pistol is lacking in the damage department. Vital Shot has a slow firing rate with weak damage and short bleeding duration, while the other abilities just don't have a lot of synergy. Body Shot is hardly used, and any buff to the direct damage of the pistol will make it used even less, as that init could be going into Unload (with the trait that applies vulnerability on crit). Black Powder, while generally powerful with other mainhand weapons, isn't nearly as powerful for pistol mainhand - again, due to the weak Vital Shot, and that you'll typically be at ranged with dual pistols than in melee range where Black Powder is best.
I like the suggestion from one forum goer, which is to make the pistol mainhand a medium/short range weapon and add a new weapon (Rifle) to fill the long range slot. They suggest giving dual pistols the Engineer treatment, where attacks do more damage the closer you are to your enemy (or just put a 600 range on them) and up the damage.
And then we'd get rifles.
Which would be totally badass.