I think they should take a note from Bronn…
Shields should always block even when they are not up, but just block if the swing hits the area the shield is covering. They should slow you down… like, a lot. Not so much movement speed but reaction time should be drastically lowered.
If you are good at blocking you can defend against two VGs and a knight with just a sword either way… I have found that shields are only useful in melee if you are working with someone (a VG, or MAA) who is using you as bait and pumping out the damage. Otherwise blocking with a sword is just as effective, if you are good at blocking. The real bonus of shields at the moment is against archers, for obvious reasons.
Letting shields block while you attack gives them an actual bonus… The downside is if you miss once, you are likely dead. This makes it more practical to have a shield, which IRL is more practical… Unless you prefer two-handers, or you are like my man Bronn and want to be really fast and skillful.
Just MHO, not looking to argue with anyone about this. These are just suggestions, take them or leave them.