Try to separate him from his turrets and wait out his shield because of the short duration of the shield. Do not let him be first on point and set up turrets.
Use your ultimate to keep people away, the optimal time to use it is overtime on center.
in case of pushing the payload, you can put it in front of the cart.
Remember to get rid of enemy deployables especially Barik's turrets and even more when he has the turret legendary card. They are not something to be ignored because when they are you don't realize when you are getting damaged