You can either:
a) Allow Barbs to dual wield 2Hers with a damage penalty
b) Simply allow 2Hers to roll 2 sockets
c) Rework Heavenly Strength to buff 1Her usage and penalize 2H damage (probably removing the reduced speed component as well)
d)Raise the damage on all 2Hers while including a more severe penalty on Heavenly Strength
e)Allow crusader shields roll +damage, but disable this bonus when using Heavenly Strength
If Crusaders didn't have Heavenly Strength they would be kinda bad IMO. The passive makes them good but still not broken. They still aren't clearing content as fast as Wizards or DHs.
As far as your solutions go:
A) If wielding 2Hs dual wield style resulted in a damage penalty then what would be the point in using them? Like say if they reduced the damage to the value where it would be the same as 1H weapons... why not just use two 1H weapons and just save up a passive slot? If you don't reduce the damage enough then just like the Crusader everyone would use the passive. Some of the stats on 2H weapons are insane. I predict that it would be a Crusader type situation where it would be mandatory on Barbs if it's good and if it's not good then no one would waste a passive on it.
B) 2H with sockets would be kinda broken. Remember 2 socket Manticore? Made every other Bow look like a joke.
C) I don't see the point in buffing 1H usage with HS... if that's the case then everyone would just use 1H with Heavenly Strength if 2H Heavenly Strength had lower damage.
D) More 2Hs have good damage the problem is that they can't compete with double sockets or 1H weapon + Source. The inherent problem is simply that Crit gems are too good.
E) If Crusader shields rolled with + damage then they would just be Sources... but better. Think about it... they would give you + damage, blocking, crit chance plus other Crusader specific buffs. It would basically be like having HS.. but without the MS penalty and the passive slot taken up.
The core of the problem is simply that Dual wield or 1H + Source/Quiver option beats 2H solo. DHs don't have to worry about 2H vs 1H, for them 2Hs are better for the most part because they can carry a Quiver (so technically they always have Heavenly Strength). If you nerf the crit gems then that makes 1H + Source the best option in the game making Wizards even more powerful. If you nerf Sources/Mojos then that makes dual wielders better.
In order to make 2Hs better while not messing up the HS balance they would probably have to nerf Source/Mojo damage and the CHD gem to the point where carrying a 2H weapon matches those combinations. If after these changes Crusader ends up being the new Wizard then slightly nerf HS if you have to.