"Guardian - An unsurpassed defender that specializes in keeping themselves and their allies safe from harm by using sword and magic. Their stamina pool is normally locked, and they must spend mana to temporarily enable it. However, all of their stamina abilities are fairly powerful in return."

It's an innate part of how the class works for Guardian-limited availability, high power.

"Warden - An offshoot of the Geomancer that has received training as a battlemage, and prefers being the middle of combat. They are capable tanks capable of providing team support, and can deal high damage to clumped enemies on their own with some setup. They have powerful abilities, but may struggle early on due to their limited resource pools."

An intentional choice, presumably to balance them being a multiclass without particular weaknesses.

Empath, AFAIK, is a Rimworld of Magic trait class, not a Kure one.

The documentation discussion link has a lot of info in it. Worth a read.