Wut? That's the most fun thing as a 2h, fighting multiple enemies.
To each his own, Xant. Regardless, dueling has always granted a bit of xp, as far as I know, and I don't think that should change in this patch. Perhaps they could simply do the following:
1. Write a script that gives a tick of 1x/2x XP to everyone on the duel server every minute, after checking to see if your character has the "dueled" flag.
2. If you have the flag, you get xp and the script removes the flag.
3. If you don't have the flag, you get no XP tick.
4. Dueling adds the "dueled" flag to your character.
OR
Just return the old XP system for duels. You kill someone? You get a bit of gold and xp.