Robots are dangerous when you start but after you find their weaknesses they are no longer scary and you can just kill them so i have some improvements.
The main issue is they are kinda weak, even on hardest difficulty. Here is some ideas that could make them a little more challenging and interesting.
Runner- not much to change, meant to be weak simple enemy. The only change is that instead of stopping to shoot you it will try and run around in circle around you kinda so it’s harder to shoot. So instead of stopping it just opens fires and keeps running around.
Hunter- Hunters are probably the creepiest enemies, big gun, giant sword, creepy noises, but once you learn that if you take off the gun and wait for them to jump so you can shoot their back they are no longer any problem. Same thing to kill them over and over. So, when they go to shoot you, they stand there for a second before they attack, like the runner, they should run around and shoot at the same time, and immediately after shooting you, they should do their jump with sword. No delay, so while they jump with sword they are also reloading. Right after they hit the ground they should do their sword swipe, just in case your still close. Then right back to shooting you and running around. This will make them a bit harder to kill. Maybe they also run faster?
Tank- it’s very easy to defeat a tank. Hide behind rock, shoot, duck. Repeat until die. Sometimes the tank will try and go around but it’s not very effective. First, the tank should have two poison grenade gas launchers, one on each side. This forces you to constantly move around to find new places to dodge. The minigun and missile launcher should also be able to find at the same time. They both have a separate cooldown and they fire as soon as they are ready. Also when the tanks alerted to a player instead of running to the location to search for person they just look at where you are and walk away. they should also have some smaller weaker turrets like the lynx on their legs. If you are far enough away they should use their run if your spotted, like if you use a radio.
Wolf- the wolf is kinda weak. It needs more health, or maybe all wolves could have the healing ability. Without it they get destroyed. The lynx have probably killed more tanks than wolves.
Like the tank, they should be able to use all their weapons at the same time, firing as soon as it’s reloaded. Maybe they could also run up to tanks and use their legs to hit tanks, have them stomp at each other when their guns are broken. It should also try and move around more.
Harvester- with the hunter changes i suggested they would become far more difficult already but they should have a little turret on them thats harder to dodge than a barrage of easily dodgable missiles.
Maybe they could learn your tactics and adapt to you idk if thats possible but would make them harder.