Hunding's Rage does not buff any weapon abilities. It should, it even says it does, but it does not. The 5 set is currently broken at the moment.
Conclusion: a crafted 6 trait requirement, 5 set bonus, that can do nothing but help any type of weapon skill or stamina build, is 100% useless.
You wrote exactly the same thing on the Hunding Rage thread.
Hunding Rage works as intended.
It raises your Ability (attack style) damage. If the damage output hits the soft cap it will scale due to the "diminishing returns".
That the melee damage cap is low, is a good argument that I will support and needs to be fixed.
Your example comparing level 13 sword to VR9 isn't consistent either. (especially on mudcrabs)
Here is my test using V5 white Maul and V6 blue GS on same V5 Bears outside Rift while I was V6.
This is with V6 blue 2H.
this is with V5 WHITE 2H maul, just an hour later on same bears.
What I found since then
a) Momentum/Rally scales better. And right now at V7 with full set Medium armour Hunding Rage, my DPS jump significatly due to a multitude of other factors
b) Attacking faster because of Medium armour
c) I have spell/armour penetration trait on the blue 2h.
d) And Hunding rage covers the damage bonus I lost from the Heavy Armour while doing styled attacks.