Hey OP, does your stamina drain when you block with a shield (if so how much)? Also how much dmg reduction are you seeing? If you hold block do you get the same benefit as timing it?
I don't think that blocking drains your stamina. If you use the block attack, that cost a bit, but much less than standard power attack. The dmg reduction ... When dual wielding, you have to avoid 2h attacks, because you can't take more than 2-3. Not at low level. When using shield or just when using single 1h/2h weapon, you don't have to avoid, you can block. You take some damage, but you can take 5-6 hits that way. And more importantly the block attack works as a short cc, which allows you to be very agressive without any real danger.
Also ... what's the advantage of having 2 weapons at low level anyway, once high enough you get the speed up, that can be nice, but at lower level ... I don't see it. WTB parrying dagger for my off hand.