I never did finish up all the calculation nor find the exact formula for any of the damage numbers. If anyone is interested in comparing here is what I found for the D2:ED:
One thing to consider with Dual Wielding is (so far as I can tell) damage bonuses (+X melee/magic) are counted twice, once for each weapon. With two weapons with good enchants/charms/other bonuses of this nature the damage you deal out can be quite substancial. By the end I was dealing 420 to 503 normal damage and 248 to 273 magic damage in melee, and I had not really pushed the stats that up damage and both swords still had a charm slot.
Edit (Math):
Dual Wielding 13: 25% / 50%
Strength: 52 * .5 = 26%
Intelligence: 42 * 1 = 42%
Right Hand: 46 to 77 + 27 (+27)
Left Hand: 27 to 45 + 59 (18 to 30 + 27)
Here are some possible formulae for max normal damage.
Formula 1: ((77 + 27) * 1.25 + (45 + 59) * 1.5) * 1.26 = 326.34
Formula 2: ((77 * 1.25 + 45 * 1.5) + 2 * (27 + 59)) * 1.26 = 389.025
Formula 3: ((77 + 27 + 59) * 1.25 + (45 + 59 + 27) * 1.5) * 1.26 = 470.296
Formula 4: ((77 * 1.25 + (45 + (59 + 27) * 2) * 1.5) * 1.26 = 497.385
The real value is higher still (by about 5.6), but the fouth formula is fairly close. It would be intersting to see how the numbers for two handed weapons stack up, if someone cares to post them.
For the diffrence between the last formula and the actual value, I suspect that at some points prior to the end the numbers get rounded resulting it the damage value being higher than it would be if it was just rounded at the end.