You people miss a key point. You don't stop behind the rock to hide from the AGT, you run your ass off, jumping when the rockets come, and you should easily survive. If you hide behind the rock, you get splash from the AGT rockets, and the guns are already trained on you. If they're not, that's an extra step you can take and that could make the difference. This is why I never mine the power plant on Under, just the open field between the plant and the tunnel. This way, if anyone tries to get through, they're guaranteed to die.