Hi. A FC member of mine noticed that Brutal Swing appeared to be doing more damage than it should (50 potency on English tooltip). He figured it to be 100 potency. We then poked around XIVDB, and it turns out that the Japanese tooltip has its potency listed as 100.
I just checked and it seems the French and German tooltips are correct (at least on XIVDB, haven't verified in-game).
edit: verified in-game the other day that the Japanese tooltip lists 100 potency.