tiny female armors!

[Vidu]

I assume thats a glamour?
In that case, your character (gender doesnt matter) is actually wearing their proper heavy armour, but are creating an illusion that they're wearing a bikini, to speak lorewise. So unless you're actually wearing some of thise skimpy clothes, there is nothing to discuss.
Most of the tank-gear is pretty heavy armor, after all - and unlike other games, where girls will get some tiny platebikini while guys get to wear the real thing, FFXIV hands out proper heavy gear to both genders when it comes to tanks, so the gender is kinda irrelevant here...

[Emstidor]

I assume thats a glamour?
In that case, your character (gender doesnt matter) is actually wearing their proper heavy armour, but are creating an illusion that they're wearing a bikini, to speak lorewise. So unless you're actually wearing some of thise skimpy clothes, there is nothing to discuss.
Most of the tank-gear is pretty heavy armor, after all - and unlike other games, where girls will get some tiny platebikini while guys get to wear the real thing, FFXIV hands out proper heavy gear to both genders when it comes to tanks, so the gender is kinda irrelevant here...

Now explain the Shisui tanking set.

[Avatre]

Now explain the Shisui tanking set.

Mystical underwater cloth that attracts metals, and is scented for the monsters to strike it only....yeah it's a stretch, but what you gonna do about it?

[Lilseph]

Mystical underwater cloth that attracts metals, and is scented for the monsters to strike it only....yeah it's a stretch, but what you gonna do about it?

I think it's one of those question that only Koji Fox can answer (and make him sweat a little). I can't find any lore related reason why they look like that and also have tanky stats.

[Vidu]

Now explain the Shisui tanking set.

Well, my personal explantion would be: We're getting this set out of a chest in a temple that belongs to people that are living in a bubble underwater because they dont care for war. So they're not people in need of plate armour and the clothes they keep in the temple are more for rituals and the like anyways.
When we bust in the casters are like "Oooh, nice, this is perfect! Has been used for rituals, filled with magic power!"
The bard goes: "Well, the colour is ugly, but its light, I can move around in this. Bought."
Melees are looking over to their tank being like: "We wont get hit anyways, right? And the bard has a point - we can move freely in this!"

While the tank stares into the chest and goes "...yeah... no one really thought about me here, eh? Okay, I'll take whats left and just..."
"...wear it at the beach only!" the healer cries out...

[Felis]

Now explain the Shisui tanking set.

That is for tanking under water