Issue

So when used on "Core Armor" the Perfect Tyrannical Gem (which is "unique") gives +6 Armor Toughness, whereas the Perfect Guardian Gem (which is not unique) give +9. It feels weird to me that the unique gem you can only put into a socket once is weaker than then not unique one.

What I'd expect

I'd expect Tyrannical Gem to either give more armor toughness / be a %, or for the bonus to be something completely different

Ah, no, the bug here is that the guardian gem is actually supposed to give Armor and not Armor Toughness. Wonder how long that's been broken.