@Cinco - I've been praising the benefits of dual-wield in DKS for ages on these forums, so it definitely 'doubles up' in DKS.
I'm sorry if my post was misleading. DW in DKS is very powerful, for a Mage or War, indeed. I fully understand that the damage bonuses, from enchants, are applied to both weapons independently. Don't get me wrong. I'm a big fan of DW, and don't have a real problem (per se) with the final outcome of it's performance. It's just every time this subject comes up, I want to question the mechanics of the damage in relation to the display. It does not work the same as it did in ED, from my stand point.
The average damage displayed would change, pending the placement of the weapon. I'm questioning if that is implemented properly in DKS. It's rather confusing. However, the bonus damage from enchants does seem to be affected by the lvl of the DW skill for a Melee Cha, from what I can tell, and yet implements the FULL effect of both for a Mage. (as you have correctly stated) Again, I don't know if the effect for a Mage was intent or an oversight.