And to be clear, those were not already in my inventory before I took on the mission, I went out to get them because of the mission

Same Problem here! I wrote the support 3 Times but don't get a reply :(

It was all the time 3 star artifact with % stat.

MartinG said:

Hello,

There is a problem with this mission, I already have two gauntlets with this requirement, but the mission is not completed. 

Hi

That item is wrong. You need to grind in sewers of arnoc you need offense type gauntles with atk% main stat.

I hope its help. 

The mission is completed by now, with gauntlets that have two instead of one star. But otherwise it is the same, for it has ATK 2% right in the title, right?

Thank you all the same for the fast reply. : -)