With the introduction of cooldowns to patrols and other parts of the game XP grinding certainly has become even harder.
Patrol xp rewards generally were reduced a bit while other areas of the game got slight boosts to xp.
Generally it still can be said that the Tau Dewa Sector patrol that we discussed here is still one of the best way to gain xp.
However... with the new sector map some new possibilties opened.
When ever you see a Tholian alert then go for it. It is currently the by far best way to gain XP.
I personally gain up to 15k xp on one run (and frequently check for these encounters).
15k is by far more than what you get during a normal mission or a patrol.
Since this is a double XP zones all the xp from killing tholian ships counts so make sure to kill as many as possible (ignore the 2 battleships until the end).
Another double XP zone are the Borg encounters.
The rewards highly depend on where these encounters take place and on how many ships you can kill.
High DPS clearly helps to gain xp.
It is possible to get 10k or more DPS out of such a mission.
Thats still about twice the amount of what you get from a patrol mission.