Ok, I dug out the episode the other night.
Firstly, I don't have a problem with Dr. Crusher as the main character here. This episode is a good reminder that Crusher IS a scientist, and that her interests are broad.
The Ferengi Scientist is a good addition to the Ferengi, laying some groundwork for Ferengi such as Rom and Nog on DS9.
But what really irritated me about this episode was PICARD. The writing for Picard just didn't add up. There are several latter TNG episodes in which Picard seems off the map, and this is one of them.
One of his most senior officers, a Commander, is conducting a MURDER INVESTIGATION that took place ON HIS SHIP, and he has little or no interest in it. He's upset at the diplomatic implications - and yet still does nothing.
Now, I realize this is a Crusher episode, but it doesn't make sense. Picard would be doing more than just offering words of encouragement. At one point, Beverly goes to talk to him in his ready room, and he says something like, "Well, you'll just have to find some evidence without doing an autopsy. Now, if you don't mind, I'm trying to read."
Another problem I have: WORF. Worf is involved with the investigation, barely, but he should have been much more into it, being as he was CHIEF OF SECURITY.
So I have to give the episode a "C" for TWO main characters being out-of-character. Crusher is believable as a scientist, I don't have a problem with that. But in order to make it a "Crusher" episode, the writers threw out what should have been the normal reactions and involvement of the other characters. Picard should have been incensed, and very interested in the investigation. Worf would have been as OCD as Crusher simply because it happened on HIS ship. We also don't have any consultation of help from Troi, who appears only to say "I sense something's up with Beverly." just before she steals the shuttlecraft. (I don't give a demerit for Troi's role, since they routinely under-used her capabilities.)