The Dagger speed nerf was uncalled for. It wasn't overpowered in PvP. The sword still is. Because the speed wasn't really the core issue. The Str Set had 1k Armor and 1k Dmg more than the other sets, which is what makes it op.
I'm guessing that somebody read somewhere "speed too high" and just assumed that Dagger was too strong as well. Then decided to alter the stat, after one look at the numbers, without doing proper testing.

OR it's a nerf for PvE cuz Ebonthrax dies waaay too fast and there are obviously way too many Mythics and gold chests in circulation, and it SHOULD naturally take 6 months to aquire a full set. You know... for fun.