Guild Wars 2

What happens when you swap classes at the very end of the match, do you still get the achievement for playing the class or must you get at least 1 point for the match to count?

I would say you are not a smart person. Asking for exploiting the game on official forum.
Dont exploit the game, you could get banned easily.
BTW, how you could swap a class in the middle of match? Dont know if its possible, I dont expect you could connect to the match with another character. Anyway, you will get dishonored while leaving the match.