Not sure what people are expecting when signing castoffs.
Sometimes, teams make bad personnel decisions. Instead of journeyman who have bounced around several NBA teams or veterans well into their decline, I'm more interested in guys who never got a fair chance to show what they have in the NBA, either because they never caught on in with a team or because they never got enough playing time for a poorly-run team. That may sound counter-intuitive, but guys who couldn't get playing time with bad teams should be looked at more closely because they are more likely to have been misused or under-utlized than players who couldn't get playing time on well-run teams.
There is a reason why finding a gem in the rough rarely happens like this -- there are 30 GMs doing due diligence in the league. Sure, you can slip by a handful of them because they're duds, but if you can play in the NBA, you eventually end up somewhere.
I agree. The general rule is that if you aren't in the NBA, you probably aren't good enough to be.
However, D-league players, usually undrafted ones, do frequently turn into serviceable role players, although almost always for bad teams.
The main exception I see are guys overseas. These fall into two categories: former NBA players who are becoming more mature, experienced role players, and foreigners who haven't been appreciated or noticed much by NBA scouts.
Players in either group usually don't have star potential, but many could play a legitimate role on an NBA team. Just this season we've seen players like Pablo Prigioni and Nando de Colo contribute to good teams as "rookies." In recent years guys like Nikola Pekovic and Tiago Splitter have blossomed into valuable players despite not having gotten much attention when they were drafted.
I think there are still only a few teams who really make the most of what overseas leagues have to offer. I don't doubt for an instant that there are multiple big men overseas who could provide valuable depth for us. But it's too late in the season at this point to sign them or make use of them.