Honestly, I realise that I am totally biased as I am an arsenal merc, however I feel that the nerf was not necessary. DfA was completely situational, it did very little dmg to grps less than 3 people. Also the 1 min CD meant that rarely was it ever used. When it did do tons of dmg was when grp of 4-5 people randomly stacked in pvp. Which is good, that's a situation where it should be used and made my class abilities mean something.
My second point was that I do not think this change was noted anywhere. I may be wrong but I do not rmbr seeing this in the patch notes. All changes to the game should be addressed in the notes, if they aren't I feel rather cheated.