I haven't had a success in such a long time, I'm sure the helmets on all my guards are really causing people trouble. They're annoying enough even on a single platform cause you have to shoot them in just the right spot to tranq them.
Yeah the decoys are excellent, throws a lot of people off guard. The fully-upgraded Stun Arm is excellent too for taking out guards since that lightning strike has a pretty good radius of effect.
The defender should honestly just fvck off after the first death. The FOB can handle itself, ever since I've made all my platforms 3 and above with max security, no one has been able to infiltrate successfully. Having a defender there just makes it much, much harder than it already is.
Use decoys, they're the best tool for FOB. I entered a medical platform, threw a decoy right in the middle and headed straight into the goal without firing a single shot.
Defender should only get one life, yep that's what I've always wanted. It's just way too easy to take down an attacker, and even if the attacker fights on for 20 minutes successfully all it takes is one explosive or a couple of sniper shots to turn great success into failure.
Single Base Development platforms are the best targets ever. I extract every container every time, unless the defender decides to show up, but I can see if they're online or not anyway before invading hehehe.