How does joinder solve the problem? You still need to motivate all those individual plaintiffs to hire a lawyer and sue, then get a court to join each one (with, presumably, opposition from the defendant every time), and then you don't have the benefit of the streamlined class action procedural rules (streamlined relative to a case with several thousand individual plaintiffs, that is). And you still have to pay the lawyers!
I'm not here to say that class actions are the best, or even a good way of regulating, but I really don't see how the joinder rules offer a useful solution.
