A missile defense is not really a solution for most of these situations.

The standard technique being used by guerillas (not just in this conflict) is to fire an RPG (rocket propelled grenade) at a helicopter hovering, or at low altitude. There is no guidance involved as such. While this requires a lot of luck to get a hit, they have a LOT of RPGs. At this point there is no defense against something like this other than to either stay out of range or sterilize the area around your operation point. Neither is practical in this case.

It isn't clear whether or not a more advanced missile system would have helped in the Chinook incident. At very low altitudes, all aircraft are quite vulnerable.

I'm hoping others who have more background in this will weigh in.