This achievement is quite hard. The team we got it with was McCree, Torbjörn, Zenyatta, and Brigitte
What to know: with each zombraider you kill, one ripe tire spawns. With each boss you kill, two ripe tires spawn.
Now, the roles:
Everyone: Any time, and I mean any time, you see a ripe tire, speak about where its at. Left, low left, middle, and right were the commands I used, but really as long as you can differentiate the possible locations you should be fine, just tell your team.
McCree: As opposed to the usual junkenstein strategy of standing on the left Bridge, stay towards the door, numbers are the key to taking out the rip tires. The ultimate charges quite fast, so don't be scared to use it, especially on road hog, symmetra, junkenstein, and mercy. Especially mercy, save your ult for the finale.
Torbjörn: Find a great placement for the turret, the far corner towards the door works. Use molten cores when rip tires are nearby the door and on any hero. Molten core charges tremendously fast.
Zenyatta: Discord rip tires and heroes as they come, prioritize the rip tires. Use the ultimate to counter road hogs ultimate and when everyone's health is low.
Brigitte: The main reason why Brigitte is vital is to lead the heroes away from the door. As discussed above, the heroes spawn two rip tires when they die. Killing heroes by the door is game over. It isn't too easy for Brigitte to lure the heroes away from the door, but if done, is the game changer. Thats the reason how we won, so certainly lure the heroes.