most of the players in 50-100 region appear overranked and suck, but there are no better players at the moment. The ones with the flukiest draws go up.
That's somewhat true because most of the players out of the top 50 have below-average records in ATP events. But there is a major difference between players like Marco C., Marchenko, Zeballos, Kubot, and then players like Falla, Seppi, Starace, Nieminen. The latter guys have proven that they can hang on the tour and win matches in ATP events on a semi-regular basis, and they dominate challengers. The former are guys who are in the top 100 based on about 2-4 good events, that they haven't backed up and show no inclination of backing up. The former are guys who have an out-of-the-blue run, an outer body experience in a way, and then crash back down to Earth and prove their true level. The latter are guys who are good players but just not quite top 50 level, but much better than challengers.