I’ve read that maps are not final. So it might be too early to report ‘falling out of map’ areas.
Nevertheless here are 2 (an a half) that I (and that no doubt other people) found.
Whitechapel
[video=youtube_share;3QGnR5JwaM0]http://youtu.be/3QGnR5JwaM0[/video]
Victoria
[video=youtube_share;-cC__DUlSCU]http://youtu.be/-cC__DUlSCU[/video]
Also, there is a wall in Whitechapel that you can walk right through, by the final attacker’s side objective (to lower the mini bridge). My guess is it doesn’t provide any cover from enemy fire either.
[video=youtube_share;rWKNziriJDg]http://youtu.be/rWKNziriJDg[/video]