Furthermore, Spell Damage, PC, denial and momentum also counter other shields (except reflectives. Jade Shield OP?) so these shields should be balanced among themselves.
Compare Titanium Shield and Dimensional Shield. While the two shields have different mechanics and thus will make them difficult to compare, PC, denial, momentum and spell damage will counter both. This means that the addition of cards that counter Shields is not the right way, as these shields should be balanced among each other. Heck, Dim Shield is even more PC-resistant than Titanium Shield. You need to destroy 6 Dims compared to at most 3 Titaniums in a deck. If you add more counters to shields in the form of PC or shield bypass or whatever stuff you may think of, the result will be like this:
5 - 1 = 4 compared to 4 - 1 = 3
Yes, I like vague analogies. They allow me to know if people really understand my argument.