BL is right: The right method is really a bit like the FW 190.
Keep your airspeed up while keeping an eye on the fuel gauge! At high speeds, the Mirage is actually quite maneuvrable, like all deltas. Above let say 400 knots you can outturn anything as fast as you.
I had the same problems as you but meanwhile I love the Shahak!
MiG-17s are still a problem, but there you simply don't dogfight at all, simply hit and run.
I score a lot of kills in Mirages, even 1967 without missiles (i modded the campaign as the IAF didnt have AIM-9Bs).
Its the friendly AI that can't handle the Mirage. Those Schmocks get themselves killed over and over again....
WOI gives you an idea why the Israelis demanded the Mirage 5: The basic fighter was just what the Israelis needed, only there was a lot of unecessary balast in form of the all-weather intercept equipment. In WOI you hardly need the radar, except in boresight mode, so you can safely throw it overboard. That's exactly what was done to create the Mirage 5