There is no perfect system. If we had a single primary, Clinton would have won it. The argument about allowing less well funded candidates participate in the small early primaries and caucuses went out the window when the media kicked a couple of the minority candidates from the TV debates in Iowa. On the other hand, there are rumors about Republicans changing to D to vote in the PA primary, which they wouldn't do if there were a single primary date.

The current system is hugely flawed, but a better one is pretty hard to come up with. Now if Clinton would just get some sense and bail out...but no, she's busy bragging about how she will bomb Iran when she's president.