A nerf is only needed if there are a lack of counters for a card in the current metagame, so that it "overruns" the majority of decks, cards, and/or strategies out there. Considering that there are SO MANY ways to deal with dims, I don't think dimsneed to be nerfed at all. Yeah, they have the potential to be annoying, but also consider the fact that ONE deflag, steal, etc. can let you OTK for the win, rendering 30-36 quanta's worth of stalling in a deck useless.
Also, on another note, there are many members of the community who support other forms of in-element PC. This would indirectly nerf dim shields as well.
...also, giving it immaterial would be a buff...