As far as the Mig 29 vs A-10, the Mig would probably either hit the A-10 BVR or if it was Remington, vector its wingman/second element onto the threat. AI isn't particularly intelligent in DCS but if you were flying against a couple of good A-A pilots online that know how to work together and employ effectice tactics, you'd be toast in the Hog.
Fighters never fly alone in the real world, so chances are if you spot one there's another not too far away and he's going to be trying his best to make your life as difficult as possible.
Then again, you'd probably never see A-10's alone in an area in which air superiority hadn't been already established in the real world. Not to mention the fact that the F-16 CJ/DJ's would have already been in to thin out the air defences.