Hello!
First off, I just want to say that I am not saying something is under- or overused, I am only stating a question about something I observed in a lot of casted games.
To the point!
Are mobile (especially UEF and Aeon) shields underused? I mean, I do regularly see Aeon players throw in 20+ shields to support a Galactic Collossus but why are they never used in the T2 stage? Of course you cannot field 20 shields at that stage, but why not just 1 or 2 alongside your horde of Pillars/Obsidians? I personally play Cybran, but I often find myself thinking how useful mobile shields would be in engagements.