You would be wrong. And I am not the only attorney that is bothered by the way this had been handled. Granted, I do not know the basis for the search warrant. However, unless there was significant evidence of significant criminal activity, I have a problem with the search warrant. A search warrant of an attorney's files and records should very limited. Maybe that burden was met in this instance. However, based on the information leaked in the press, it does not appear to have been sufficient in my opinion (and in the opinion of other attorneys I have talked to).
As for revealing Sean Hannity as the third client, I have a bigger problem with that. It should not have been disclosed publicly--and the widespread reaction to that revelation is precisely why it should not have happened. Yes, a client's identity is normally not considered privileged. However, that is not the end of the discussion. Courts can, and should, protect confidential information even when it is not protected by privilege--and that includes the identity of an attorney's clients (assuming that the representation is not already a matter of public record, widely known, etc.).
Imagine the Cohen were a well-known, high-powered divorce lawyer in town, and you retained him last week to file suit for divorce from your wife. Would you want the fact that you are a client of that divorce lawyer disclosed in open court, and then published in the local paper? Of course not. I'm no Hannity fan, but his identity should not have been disclosed in open court.