The best medium armor for survivability against the automatons is on the Superstore until 10 AM GMT Tuesday.

The Superstore is currently selling the B-24 Enforcer medium armor for 150 Super Credits, for the next 13 hours as of this post (until 10 AM GMT on Tuesday if I have my timezones right).

It is the only medium armor that has both >100 armor rating (has 129) and the Fortified passive. Going above 100 armor rating on your armor means you take less damage from headshots, and the Fortified passive gives you 50% resistance to explosive damage (plus 30% less recoil when crouching or prone). Both tremendously boost your survivability against Automatons!