Take the white minimum and maximum damage numbers, right under the words "Damage Per Second" in the item box, and add them. Then divide by two. This is the average damage the weapon will produce per hit. Now multiply the average damage by the weapon's "Attacks per Second" value. This is the derived DPS value displayed in huge white font at the very top of the item box.
In this case that is...
((1276 + 1722) / 2) * 1.4 = (1499 * 1.4) = 2098.6
Now, if you reroll the damage range to add 100 to the maximum and 50 to the minimum, those numbers will change as so...
((1326 + 1822) / 2) * 1.4 = (1571 * 1.4) = 2203.6
If you roll the VIT to 10% dmg, you, obviously, add 10% to the average damage value...
(((1276 + 1722) / 2) * 1.1) * 1.4 = (1648 * 1.4) = 2308.46
Thus you will gain significantly more DPS by rolling VIT to 10% damage. Whether you absolutely require VIT on your weapon rather than raw damage I'll leave up to you to decide. I will say that your weapon is your primary source of raw damage, one of the most important values in the entire game for most classes, a value impossible or difficult to obtain in other slots. While it is possible to find the average damage stat on jewelry and off-hand, average damage on jewelry loses out to more desirable possibilities such as crit chance, crit damage, cooldown reduction, and so on.