Well, the main role of the aircaft is ground strike but if there are not interceptors availible, they could send an AJS37 with 6 sidewinders, using his radar alongside the GCI to intercept the bandits (Bombers or helicopters)
In the case you are chased, you can always run away but you can also defend yourself with more chances of survival than in a F5, using the massive speed but as always, is not recommended.
Anyawy, if you can bring down an F15 with a 21, you can always take down a Su-27 with a Viggen no probs if you stay hidden but thats not your role.