[Senna]

The points above were already on the money. Guard is very spammable and more than 80% of the weapons type in the game are melee base so they're always suffering from it. We have guardbreakers but it's not something you can always use or prepared to use every chance you have, especially since you'll be wasting 3 momentum, 6 if you have to move while they could do whatever they need to and guard with 1 momentum.

Drifting aside, Increasing it to Guard LV30 seems nice or let it work like the mirror knight whereas taking physical (Or magic) damage breaks the mirror until they guard again.