Proto Set both triple maxed with various status and damage defense UVs, CTR VH + ASI VH Proto Sword and Proto Guns, CTR VH Proto Bomb.

Let's see, shields are most often needed 1) to withstand bullet hell, 2) absorb shock pulses, 3) block spikes & brambles, and 4) absorb massive whacks. Hence: a Grey Owlite Shield with pierce, stun & poison max. This shield will block spikes, brambles, poison brambles, shadow fire, shock damage, and massive Vanaduke hits. It's your everyday hazard-avoidance shield.

Now, the only statuses the swarm ever gives your are poison & stun. These two statuses never come together, so one of them has to be a UV. According to the wiki, the Void Gel deals only piercing with poison, the Void Wolver and Lumber deal only normal with the latter dealing stun, and the rest deal split. The pure damage voids are the most threatening. So we're looking at a shield with normal, piercing, stun, and poison. Hence, the Ironmight Plate Shield with UV Poison Max.

To best resist the enemies in FSC, you're going to need normal and shadow to block trojans, normal, elemental, fire, and stun to block Vanaduke's mace, elemental and fire to block Vanaduke's bullets, normal, shadow, and fire to block zombie swipes, normal, elemental, and fire to block rocket puppy shots, and elemental and fire to block Red Rover flames. So the damage in question involves normal, elemental, shadow, fire, and stun. I'm gonna say Grey Owlite with UVs shadow & stun max. I was going to suggest Volcanic plate with elemental and shadow max to best resist heavy smashes, but Vanaduke's bullet hell, those darn Rocket puppies, and the rare heavy melee smash make a more convincing argument for Owlite.

For PvP, movement while shielding/cloaking is highly valued. Flourishes, Gran Fausts, Rocket Hammers, and Polarises are common. Shock, Freeze, and Stun are the deadliest statuses. ASI and damage bonuses are highly valued for most classes, but CTR is more valued for bombers. With so many damage types to be concerned with, which set offers the best bang for the buck??

Enter Mercurial Demo. Tack on UVs pierce, shadow, & freeze max, and you're all set to go for either guardian or recon. Guardians will like it for the faster movement while shielding, and the recons will like it for that reason too, plus the bomb damage bonus it offers. Since guardians also get a bomb charge time reduction, they too could conceivably benefit from the bomb damage bonus, but in practice, it's not useful. But this isn't the ideal Striker set.

For Strikers, Skolver with elemental, shock & stun max is preferred. I chose elemental & stun because 1) you might find yourself accidentally running into hazards, including spikes which deal stun, 2) Polaris users; 'nuff said, and 3) Stagger Storm users might be trying to adapt. Shock Max is a no-brainer. Of course, shadow damage will still be a weakness of yours, so you could put elemental on one piece and shadow on another.

If you're a gung-ho guardian, try on an Ancient Plate set for size. Put on max UVs for all three special damage types, and you'll be one mean tanker. Statuses will still be your greatest foe, but you'll be shielding against those, right?...right?...no? Then you could swap out the damage types with shock, freeze, and stun if you insist.

Very well thought out, Thinslayer, -at least all in theory- but Derpules is right about defence UVs being fairly limited. It's good not to rely on UVs entirely for defence as you'll find them amount to very little on your character overlay. It's best to allow it to just stack up on top of current defences.
And A.Plate is a completely UP set; the normal defence doesn't save you from much and a lack of special defences leave it more fragile than most. And I may be wrong, but I'm pretty sure that a full set of A.Plate has some redundant normal defence anyways, meaning you're better off with just one part A.Plate and another part of [something better].

It would give you the extra tanking power of a hit or two (short of heavy swords, which it'll probably have zero affect upon) and the health will be nice, but with no special defence at all it'll still tear apart pretty easily. As a gunner I switch to my umbra to charge and you can immediately tell the difference between hitting Skolvers and Snarbies, and those guns have low damage per shot, compared to heavy weapons like GF; s'why they're so popular: someone with zero shadow defence gets destroyed by GFs.

Full Mercurial Demo
-Freeze Max
-Fire Max
-Stun Max

Ironmight Plate Shield
-Fire max
-Shock max
-Elemental Max?

2x Elite Boom Module

Dark Briar Barrage
Electron Vortex
Dark Retribution
-CTR very high for all of them
-No other UV would matter

Valiance
-ASI very high
-CTR very high
-Construct damage very high