As I mentioned earlier this bug was for situation when you locked the screen with Super+L or Ctrl+Alt+L or from indicator-session monitor never blanked off.
It is now fixed and when you lock the screen with any of the above mentioned methods monitor blanks off after 2 seconds.
Any problems with multimonitor setups or screensaver not blanking the screen should be reported as new bug.
As I mentioned earlier this bug was for situation when you locked the screen with Super+L or Ctrl+Alt+L or from indicator-session monitor never blanked off.
It is now fixed and when you lock the screen with any of the above mentioned methods monitor blanks off after 2 seconds.
Any problems with multimonitor setups or screensaver not blanking the screen should be reported as new bug.