Banner mastery + valour = enemies take 90%+ increased damage?

There is a banner mastery that provides "banners also cause enemies to take 8% increased damage". Path of Building's Community Fork just updated, and it's showing that this effect scales with valour, the the effect of making enemies take over 90% increased damage at 105 valour. This is on top of the banner's own innate effect that gives over 60% more phys damage at 105 valour.

Is this the intended behaviour of the mastery (which doesn't seem very balanced for the small investment of about 10 passive points needed, you can gain valour pretty fast with warcries and during content with high mob density), or does the mastery effect not scale with valour and stay at 8%?

With the new Perfidy this would become even more broken. I'd like to know if this is how it's supposed to work, as it would dramatically change the damage certain melee builds can deal.

Is there any chance we can get a clarification for this? It will make a massive difference in terms of the damage certain melee builds can deal. If this is the intended interaction then we are back to needing to read a wiki/guide in order to properly scale melee damage, which is the opposite of what Mark was saying when he described the methodology behind the melee changes, as it's unintuitive for the average player.

Builds based around selfcasting multiple warcries are already dealing good damage with the changes, and they would be able to sustain a banner often due to the warcry+banner synergy mastery and regularly gain somewhere in the region of 124% increased damage taken by enemies with low investment, on top of the innate effect of the banner they use. The precedent for aurabots is also very important here, as is the ruthless version of Champion's Inspirational node which grants the same effect as Perfidy, opening up another abuse case.