That said, yes, of course Shields are useful to all classes because "duh." My argument was never "Time Mages in no way benefit from Shields". It was (and still is) "Time Mages only really benefit from two Shields--Aegis Shield & Genji Shield--without having to dip into specific secondaries".
I argue that all classes can use all shields equally well. The elemental resistance from Gold Shield, Platina Shield, and so on are universally applicable. P-EV and M-EV are also universally applicable.
Like I said in my previous post, the shield serves a second purpose: boosting the Time Mage's lousy stats (or, alternatively, providing some elemental resistance). Stat boosts and elemental resistances apply whether the Time Mage is mid-charged or not.
In the end, the purpose the shield is put toward depends entirely on the player.
I'm now going to go through a list of the non-Aegis, Genji, and Zephyr shields and see which ones require a secondary to take full advantage of.
Mythril Shield: 15 P-EV/20 M-EV, Absorb Earth Weak Lightning - no secondary needed
Gold Shield: the compliment to Mythril Shield, also no secondary needed
Ice and Flame Shields: Similar to above, just with Fire/Ice Absorb/Weak, so no secondary needed here
Diamond Shield: 5 P-EV/25 M-EV, Null Earth and Holy - no secondary required
Platina Shield: 25/5, Null Wind and Water - no secondary needed
Crystal Shield: 20/20, Neutral: All - no secondary needed
Kaiser Plate: 15/20, Strengthen Fire Ice Lightning - yes
Escutcheon II: 25/25, no secondary needed
So uh, only one shield needs a secondary to be extra effective.
Also, I think Genji Shield is a rather poor choice for a Time Mage. Genji Shield has very meh evasion, and the main reason to use it, the +1 PA, does not benefit Time Mages. The Cancel: Dead (and by extension, Death Sentence (I think?)) part is nice, but it's not very common. Death Sentence, Secret Fist, Throwing Knife and Odin IIRC are the only ways to inflict Dead/Death Sentence. Oh and Death, which apparently requires the target to be susceptible to Dead.
As for why Paladins "should" have Shields if they access to Mantles as well, it's because a) they're meant to be defensive tanks and b) they have no class evasion anymore to make up for having access to both. Remember when they had just decent evasion, barely more HP than I had now and access to both Shields & Mantles? When they still pretty much beat the shit of everyone else despite having a crappy skill set aside from Grand Cross before Blind was buffed? Yeah.
They were only able to 'beat the shit out of everyone' more because of their stats than anything - they had 12 PA at the time. That's 2 PA more than they have now. That's actually relevant, since before you could give them Attack UP and they'd already be at an effective 16 PA, so you could give them non-stat boosting armor, knowing they would do solid damage.
I'm pretty sure Paladins lost their C-EV (which was only like 5 or 10% at the time, anyway) because it was a small and simple nerf that wouldn't change things too much, and it was part of the main nerf package of adjusting their stats in the first place. If it was due to them having access to Shields and Mantles, then most likely Abandon was the problem, as Abandon was 2x evade for a time.
Now that Paladins do occupy a more defensive role, I think it would be ok to give them some C-EV, just 5 or 10%. Remember, C-EV only applies to physical attacks coming from the front (unless you use Awareness). Chances are good that a unit will face a few physical attacks from the front, but it's usually inconsequential, as units also have innate Weapon Guard (which also may or may not be fairly inconsequential). If there's a significantly higher chance to miss, it's likely due to Shields and/or Mantles and/or Main Gauche than it is C-EV. I think Thief C-EV is fine for said reason - they have access to Main Gauche for a really slippery unit, and Concentrate and Hidden Knife are around to counter.
Also, as a fun sidenote, the spellguns are actually working as intended. The changes were meant to encourage people to shoot things with it, instead of comboing them with other skills due to their formerly absurd WP. Their WP was that high to begin with to make the average damage from a spellgun shot reasonable, since 60% of the time it would fire off a tier 1 spell.