Well, it very much depends on the situation.
First up, the Mirage can carry up to 6 missiles, 4 Matra Super530D's and 2 Magic II's.
The RDY radar is pretty decent allthings considered, having a range of 120 km (if the manufacturers advertisements are to be believed.)
Now your Magic II is your pretty avarage close in IR missile, 15km max range, so pretty comperable to the US IR AIM missile, with the exception the French have a thing for Mach 5 missiles.
Likewise the Matra Super 530D is a 40-50 km missile, with a top speed of, again Mach 5, but semi active. For Comparison, the US AIM missile tops out at Mach 4, and the R27 at Mach 4.5.
overall, it isn't too bad, its pretty much in line with what the rest of the world used in the 80's. So overall i think, that it stands a pretty decent chance all things considered, especially since Jamming and a small radar cross section make detection harder, partly compensating for the slightly less then stellar missiles.
@Dartuil
Interesting you mention that.
Hope that clears things up :)