[Neus]

A few responses;

I'm not married to the reduction amount of 50%. It could also be tiered to be partial-glancing with a lower reduction within a certain range, as was suggested.
As far as critical hits go, look at the last bullet point in the OP. Basically, if your attack hits but is a glancing blow, it will not critically hit.

It wouldn't work with parries for sure. Other reductions are a maybe. I could see it not stacking with most of them, for example Evasion wouldn't make sense.