Since posts about this issue don't get answers, I made a ticket about vanish not working versus city guards. (We all know the issue: The just ignore the vanish, and keep running after you, even if they are like 30 feet away, when you vanish.)

The conversation:
http://img7.imageshack.us/i/vanishguards2.jpg/

Well you can see it for yourself. It's our fault. It's the lag that causes guards to ignore vanish even if they are half a city away. -_-

EDIT: edited the screenshot for 'naming and shaming' reasons