Honestly, while the vorpal weapon damage looks potentially huge, it doesn't work out that way if you do the math. In the best possible case -- using a vorpal falchion (2d4) with gauntlets of destruction (reroll all 1's) -- you raise the average [W] damage from 5 to 9. Just using a weapon with 2d6 base damage would give you average [W] damage of 7. It's still a good combo, but it doesn't seem overpowered for what you're spending.
Math on the 5 -> 9 [W] damage:
A basic falchion is 2d4, with an average of 2.5 per d4, so 5 average damage total.
Rerolling all 1's means that your possible results are 2,3,4 on each die, and that gives vorpal a 1/3 chance of granting an extra roll, then a 1/3 chance of granting an extra roll on the extra roll, etc. That works out to 1 / (1 - 1/3) = 1.5 rolls per die on average. With possible results of 2,3,4, the average damage per die is 3, and the rerolls boost that to 4.5. A falchion starts at 2d4, so that's a total of 9 average damage.
If you're using a vorpal falchion without the gauntlets, the average [W] damage is 6.67, which is less than a non-vorpal 2d6 weapon.