I don't disagree that the episode wasn't as good as others.. but where in the 'season' should they have put those normal cases? It's only a 3 episode season. The other cases being in the first 2/3rds of this one episode is the equivalent of two episodes in a normal half hour show.
That wasn't the problem with the episode, it was that the mysteries themselves aren't as well planned out as previously. The actual 'crime' isn't being introduced until later in the episode and then solved immediately. There's no buildup of it, nothing at stake. Yes, they were technically all related, but it didn't feel as clean as previous episodes. It felt like two mini mysteries crammed into a 3rd.