Vargo said:
Have you thought about setting the DCs to something like 10+(d/v) where d = damage, and v = some number like 5 or 10? 10 would be very good, as it would keep the DCs reasonably low, the math easy, and the game fast.
Mathematically, that's very elegant--probably the /5 version gives better numbers, but i'd have to sit down and do some figurin'. However, as a practical matter, i think it'd be too awkward. At least with my group, keeping track of the various options this presents, just in terms of when it's best to go for big damage, and when to go for big crit, is plenty. Not only would you have to calculate these DCs on the fly, but it would add in the question of trading off likely damage for save difficulty--and in a non-obvious way, IMHO--to the calculation of what grip to use.
So, in short: brilliant idea, wish i'd thought of it; but i don't think it would work with my group, at least.
Using BAB is, in this case, i think, a reasonable compromise: it reflects general martial prowess, if not the specific effectiveness of the attack or the grip chosen, or the size of the weapon/wielder. On the downside, you're giving up some verisimillitude. On the upside, it helps reflect the "skill trumps physics" feel of the system in general, by not further disadvantaging small wielders (who would have lower save DCs on special effects, in addition to lower damage to start with).