Basically what LeyrHao said:
Passive: The way of old:
When weilding a two handed mace, axe or stave....
-Your lava lash deals damage as if weilding an offhand weapon off the same item level
-Both Enhanced Weapon and Unleash Elements effects are applied to your two-handed weapon
-Your maelstrom weapon proc chance is increased by 60%. (up to number crunching, but with slower speed and half the attacks, we'll maybe need even more than that)
-(only if weapons are still based (and set) on primary stats): Strenght on the weapon is converted into agility
Would there be anything else dw-specific?