It's not specific to 2.5 but dual wielding with elemental weapons is still broken.
What happens is that if your main hand is an elemental weapon, equipping a second weapon, physical or elemental, disables the innate dmg of your main hand.
So dual wielding with a main hand elemental weapon actually decrease your DPS, and by a lot since it's the weapon used by your skills.
It may seem minor but i think it's a shame because there are a few scenarios when I would prefer to not have any block, which is harder when you can only equip a shield, or lose a whole equipmnet slot.
And dual wielding is cool