The Impaler Keystone preventing impales

Setup:
100% chance to impale with attacks from the passive tree and gear.
Mastery: "Impale damage dealt to Enemies Impales by you ignores Enemy Physical damage reduction"
Alocated Keystone: The Imapler
1 singular target for visual clarity
Level 21 Sunder with a high dmg Karui Chopper for a big single physical hit
Level 1 Stormbrand to hit enemies with a near 0 damage skill.

Expected result:
I hit the enemy with Sunder -> Enemy gains 6 Impale stacks ->Stormbrand hits enemy regularly and impale stacks get used for 10%*#of impale stacks(6)*#of hits the impales last for(5)=300% dmg of the initial hit

Observed result:
I hit the enemy with Sunder -> No visual impale stacks on the enemy -> No further damage dealt is observed while Stormbrand is attached.


Comparison without "The Impaler" allocated:

Expected result:
I hit the enemy with Sunder -> Enemy gains 1 Impale stacks -> Stormbrand hits enemy regularly and impale stacks get used for 10%*#of impale stacks(1)*#of hits the impales last for(5)=50% dmg of the initial hit

Observed result:
I hit the enemy with Sunder -> Enemy gains 1 Impale stack which also can be visually seen -> Stormbrand hits enemy regularly and impale stacks get used for 10%*#of impale stacks(1)*#of hits the impales last for(5)=50% damage of the initial hit

Further testing in pvp revealed the following behaviour:

100% chance to hit with resolut technique
100% chance to impale
enemy has 0% chance to block or avoid impale
The Impaler Keystone allocated

First hit inflicts 6 Stacks of Imaple which seem to deal the correct amount of damage. After the first hit it becomes impossible to Impale the enemy at all.

When unallocating The Impaler the behaviour is observed as expected.