Correct, there is no talent that requires you to have withcraft 5.
Man at arms does have level 15+ skills, namely: nullify resistance and terror both which require level 16.
Expert Marksman does not have skills after level 13.
If you missed the man at arms skillbooks you might have been unlucky, vendors spawn their skillbooks random, so there is a chance you just haven't seen it spawn yet. Before talking to a vendor you can quicksave the game, if he doesn't have the book you need, just quickload and repeat untill he has the book you want. (Keep in mind that not every skillbook can be purchased, however the 2 mentioned above can.)
With kind regards,
Rashar.
Last edited by Rashar; 07/09/14 11:53 AM.