That's just the way things go sometimes, you have to remember that there are 9 other sets in fk. We don't definitely know the droprates of any of the sets, but it takes a large number of runs to generate a big enough sample size. Unfortunately the players who usually will have better luck than others don't report anything about it, so it looks worse with only players experiencing negative outcomes saying something.
Unlike the shard pull, there's actually no official drop rate from Plarium about artifacts from dungeons.
People assume it's an equal drop rate for all type of sets, while I think certain sets drop more rarely than others.
So until Plarium actually release an official drop rate numbers of this artifacts just treat these "drop frenzy" events as just normal day... Because we really couldn't calculate anything anyway.