Sword-Oath Translation

Translating the original japanese description word by word:

"Whenever you auto-attack, you will deal additional damage."
Potency: 50 (this potency text is the green one in all damage ability tooltips)

Current english-translation:

"Increases the potency of auto-attacks by 50."
(No green Potency: 50 text at all)

Ingame behavior: Whenever you auto attack, an additional attack with potency of 50 is triggered.

The japanese text makes it clear that it will trigger an additional attack, while the english version makes it sound as if your autoattacks will deal more damage.

Further the english translation completely removed the green "Potency: 50" text.

I don't think the Japanese text is any more clear on what happens. That is, reading your translation of the JP tool tip, I get the same impression I do reading the EN one. That said, they should both be changed to make it clear that an extra attack is happening, I'd say.