At the time of writing this I haven't played the mission where you get the plague buster yet, but I find that the easy way to kill Juggs is by driving a vehicle at them - backwards!
By driving hitting them with the rear of the vehicle you don't take any, or barely any, damage unlike hitting them head on which is a sure fire way to wreck your ride. As long as you have a bit of road or space to do it, just reverse into the Jugg, quickly drive forward again before it hits the car, rinse and repeat, it usually goes down after 8-10 hits. It can also be done in the small car, it doesn't have to be a heavy vehicle although a truck seems to make it a bit quicker. I've pumped round after round into their face with little effect, but reversing into them makes short work of them.
This method of vehicular slaughter with minimal car damage can also be applied to killing all zombies, including ferals (although they often dodge out of the way so you need to be quick with them) and is especially effective for hordes.
It also means that you don't get your Jugg or feral kill stolen from you by your AI partner because they'll be in the car with you.