Wow I have never seen this level 24 version of the Last Stand. I have gotten plenty of the lower level ones but never used it. I don't have the Dancer Axe or the Hakkon but this seems like a cool weapon for the Reaver at 330 damage which is as high as my highest damage Dragon Maul. Reaver with constant guard and low health = high damage and safety net!
OP you said guard generation works on the Katari, but doesn't Katari generates guard on any weapon on hit just like the Silent Sister? I don't play Katari normally, but the few times I did, I noticed the guard on hit. So maybe the weapon is just broken for everyone?