Guild Wars 2

the hot-key to choose the nearest target function is broken now.
it never works if you already have a target.
this is an important function, please fix it.

If your issue you are describing is that it will no longer target the nearest enemy if you have a champion enemy targeted, or if a champion enemy is on your screen then it will only target the champion instead of a nearest enemy, then:

This issue had been reported by others since the change to targeting was made last month.

Reported Functionality Issues (Hover on INFO for issue description)

• Controls – ‘Target Nearest’ Overridden By Champion Presence
  | INFO | Report Thread | Dev Response |

Pulled from the Tracker: Reported Bugs and Their Status [collaborative effort by players] sticky thread.

Yeah, tab-targetting is even worse than it used to be. Kind of sad.