I'm glad that this game is inspired by M&B. Great combat system. I know though that there is some debate over wether shields should be 100% block rate or not, and I have a solution.
My idea: Along with a 100% block rate from a shield, shielding would only last for a DURATION, depending on modifiers (eg. constitution, health, stamina).
This would make combat very exciting and realistic IMO. One would have incentive to block knowing that they will be fully protected, but they will want to block for as little amount of time as possible. Blocking quickly as a reflex would become the norm, so as to sap as little energy as possible, rather than hiding behind your shield.
Shield block duration could be based on anything you guys thought appropriate. It could even be a whole new stat/skill.