There are over a 100 vehicles and one ruins the game for you? I'm not sure exactly which vehicle you are talking about but I've been in a half track, armored car, armored van, armored apc, and my preorder Monster truck and all can take a serious pounding. Maybe the vehicle you are using isn't an armored one but just looks it?
Not really sure as I still have over 70 vehicles to drive. So maybe there really is an armored vehicle that is paper thin. But just saying don't let one vehicle ruin the game for you.
It was the mission where you had to deliver the Armored Vehicle so you had to drive it,I figured a way through it finally,I just stopped each time they shot at me and got out and killed and blew up everything in site with the rocket launcher.