Diablo 3 Weapon Damage Range

Solution 1:

I think you have your order of operations wrong. The 50% bonus should be applied last. Take a look at the image you linked. The base damage possible for the axe is 507. If you multiply that by 1.5 and then add 282, you're still well short of the minimum damage displayed on the weapon. But if you instead take 507 and add 282, then multiply by 1.5, you end up at 1183.5, rounded up to the 1184 displayed on the weapon. 1185 + (373 * 1.5) gives you the 1744 top end.

So (507 + 286) * 1.5 = 1189.5 as the min damage. That gets rounded up to 1190, and the max damage has to be higher, so it starts at 1191. 1191 + (381 * 1.5) = 1762.5. Note that the delta is meaningless here, because it is lower than the min damage boost anyway.