So there are are quite a few shields in spiral knights, but some will probably never get used because they are simply worse than others.
Piercing Shields:
Aegis vs Barbarous thorn shield vs Ironmight vs Royal Jelly.
All are probably outshined (for swordsmen) by the BTS providing good defence and a very enticing damage bonus.
Ironmight has large very good normal defence and ok pierce, with stun resist so good overall. Royal jelly perhaps being overshadowed by this with more piercing but a lot less normal defence, with the addition of sleep defence, might become more useful if sloombargos ever return but currently not so good. Out of them all aegis has no status resist and is considered inferior in some way to all of these.
There are the shadow shields:
Dread skelly vs Crest of Almire
Here, both are good shields providing either stronger shadow defence or a balance of both normal and shadow with useful resistances, arguably CoA providing the more useful but both good shields none the less.
We have the general purpose shields:
Volcanic Plate vs Omega shell vs Ancient Plate
As discussed before (in other threads I mean) some do better in certain areas than others and so comes out reasonably balanced, all being able to do the same thing being OK everywhere, and doing especially well in t1/t2. Volcanic plate's fire resistance is especially useful for use in FSC.
Perk Shields:
Barbarous thorn shield vs Swiftstrike vs Scarlet
Here, scarlet is simply outdone, offering little bonus compared to the other two and so useless in tier 3. Arguably swiftstrike provides too much bonus for the defence it provides but it does require skill to use in areas of danger.
Elemental Shields:
Grey Owlite vs Heater shield
Grey owlite provides good elemental defence, ok normal defence but most importantly protects from 2 of the most prominent statuses that elemental monsters deal that are arguably most dangerous. Heater shield has ok elemental defence and good normal defence, but provides a single status defence to freeze which makes it very situational. Simply outclassed by the owlite.
Dragon Scale Shield: Comes into it's own league in C42 mission and has fire resist as well as elemental, making it viable in FSC. Plus it looks amazing. Without any normal defence, however, it is rather useless most places.
So shields that probably need to be reworked to either make them more viable or less ideal for everything: swiftstrike buckler, Barbarous thorn shield, scarlet shield, aegis, heater shield, and royal jelly shield.
Anyone else have views on this?
I haven't read your comments in detail, but I agree with the general idea that the shields could use some balancing.
You point out that Dragon Scale is good in C42 (no argument there), but you fail to point out that it's terrible elsewhere.