There are 2 problems here. (1) The c# .NET implementation is lacking; (2) the fundamental crypto design of the kdbx database (which is shared by all implementations, in any language) is lacking.
Yes, but since this isn't some networked service I'm not as concerned about the general quality of the code. Offline attacks really have to focus on the encrypted password database. If an attacker has local access you're already owned -- they could just modify the application to do whatever they want... or keylog you, etc.
The safety of your database in a world where your keepass database is leaked due to a Dropbox attack or something is what really matters here, IMO.
Did they screw up the crypto so offline attacks are easier?
It's not 100% offline. As you said, if they manage to access your Dropbox, they could theoretically sync an altered database back to you. If the application leaks some information while attempting to open the database or can be made to leak information, that would be bad.
