Skull shield could use a buff I think. It cost is = to fog shield but due to it's element it will never be used for anything good. Also it is not nearly as good as Fog shield.
Due to the element that Dusk shield is in and that it makes 50% of attacks just fail I think it should be nerfed. Devourer, dagger and vampire are all really good but missing with 50% of your attacks too? Up the cost by 1.
Reflective shield could reflect more stuff or give it another skill like solar shield but the cost would also have to boost up.