I’m primarily an arcade player, so cannot speak to the Mirage F1C and CT performance is RB/SB, but in AB, this aircraft is dramatically and unrealistically underperforming relative to other aircraft.
These aircraft have a displayed rate of climb (fully spaded) of 186.5m/s in AB. After some testing, this is pretty much in-line with my experience in-game.
According to Dassault’s fact sheet, the Mirage F1C has an initial rate of climb of 210m/s at sea-level, increasing to 245m/s at altitude, a full 24% increase over it’s current performance in AB. Additionally, testing with the (unified) German and South African air forces reported the Mirage F1C as having “significantly higher” rate of climb and sustained turning capability compared to the mig-21bis - this is the opposite in War Thunder currently. The mig DRAMATICALLY outclimbs and outperforms (in terms of energy retention) the Mirage F1.
http://all-aero.com/index.php?option=com_content&view=article&id=2767:dassault-mirage-f1&catid=45