questions

I just got my first shield and realized the enemy attacks twice in a row compared to my one attack. I should have figured. At what percentage does a shield become viable? Compared to two handed.

anything over 50% block chance in the workshop is suitable.

I think it is 55%-60%.

Logic tells me that if you have a better chance of blocking than being hit then it makes sense although I might be wrong, myriad or someone like that probably knows.

It's not a set number like 50%, its dependant on a lot of factors like the additional armour you may gain, weapons and even opponents build, but a general rule is shields tend to start being worth it around 200 dex