Those are good frame rates without knowing your settings. Monitor your temps to see if there is possible gpu or cpu throttling issues.
What is the screen resolution? What are the graphics presets for BF4?
I can tell you right now that a 270x running BF4 @1080p on High settings will average 68.8 fps and Ultra will average 43.1 fps.
The screen resolution ist 1680 x 1050 60Hz because I have an screen that ist a little bit older.
The Settings are my own setting based on High, some settings are only mid.
With this settings i played normaly between 100 and 120 fps when Mantle is on. Without Mantle I played 85-95 fps. The same problem i´ve got in BF3 so I don´t think that it´s a problem based on the presets, because these lower fps I became first with Catalyst 15.7, with the old driver there were no Problems an the graphics presets are the same as before.
I´m monitoring the temps next time but i can´t belive that this is the Problem