The Best Practices Guide says "Check that every administrator that needs to log on to the Object Directory goes through the Endpoint Encryption Database server, not direct through local connection." It doesn't explain this recommendation - what are the effects of using a direct connection?
there's no physical access right arbitration when you use a direct connection - that's provided by the database server itself. Plus, it's best to funnel everything through the server so you can optimize access.
You should certainly never be sharing the folder your data base is stored in off machine, that will pull the performance down to almost nothing.