Are +maximum damage and +minimum damage enchantments factored into weapon DPS?
Yes, they are. The easiest way to check this is to find a weapon with a socket, since you can manually add +min and +max enchantements to them. Now add a Ruby to it (enhances damage by a certain range). You will see the DPS go up in the item tooltip.
Also, it worked the same way in Diablo 2, so it's likely that they simply just left it the way it was.