It's actually way too easy and I don't see how anyone else figured this one out..
1) Get Heavenly Strenght - Equip 2H + Shield (with a legendary affix, such as the condem one)
2) Replace Heavenly Strenght with another Passive
3) Shield stays equipped but gets the red border + locked icon, not adding the stats to your character. However, the Condem effect still works. which removes the cooldown.
4) More damage because the Heavenly Strenght Passive is gone!
I haven't tested any other skills, but I figure this should work with any other shield that changes a skill.