I've been playing since last February, about 600 hours now. The matchmaking system throws you into all sorts of squads. Sometimes four people bring random loadouts, land and start shooting chaotically, with maybe a 50% mission completion rate. Sometimes you get a squad with good coordination, and even difficulty 9 goes smoothly.
What's the difference? Loadout composition and positioning.
There are two aspects to this: how to choose stratagems based on mission type, and how to find your role in random squads without voice chat. I've discussed these with quite a few people in HD2 Discord channels. What I'm writing below is what I've figured out through my own experience.
A lot of people fill all four stratagem slots with damage. Machine gun, recoilless rifle, railgun, 500kg bomb. Plenty of firepower, but when heavy armored units group up and your cooldowns don't line up, all you can do is run.
I now always bring one support stratagem. Supply pack or shield backpack. The remaining three slots are chosen based on the mission.
The flamethrower works great against bugs but is basically useless against robots. The recoilless rifle is the opposite—one-shots robot tanks and walkers, but takes two or three shots for large bug units.
The supply pack is more practical than the shield in bug missions. Bug attacks are mostly close-range physical damage, and the shield breaks after a few hits. Robot lasers and bullets can actually be absorbed by the shield, giving noticeably better sustain.
Without voice chat, teammates won't tell you what they're doing. But you can see what equipment they brought.
After landing, take a few seconds to look at your teammates' stratagem icons. If someone brought a machine gun turret and mortar, they'll most likely find a high point and hold position. If someone brought a jump pack and shotgun, they'll be in enemies' faces.
Your position depends on them.
If the squad already has two long-range damage dealers, don't bring another railgun. Switch to EAT or recoilless rifle to handle heavy armor that slips through. If everyone on the squad is rushing in for close combat, bring a machine gun and stay in the back to clean up wounded enemies and small mobs.
One detail: blue markers on the map. Experienced players use markers to tell you where to go next, or where enemies are. If you see a teammate ping the same spot three times in a row, that means they want you to go there.
A lot of squads die during extraction. All objectives completed, then wiped during evac.
After the extraction signal is sent, there's a 90-second wait. During these 90 seconds, three to four waves of enemies will spawn.
Don't bunch up all four people in the middle of the extraction point. The shuttle's approach direction is fixed—you can see the arrow on the extraction point on the map. Stand on the arrow side, with your back to where the shuttle comes from, facing the enemy spawn points.
If someone has a shield, let them stand in front to absorb the first wave of fire. Everyone else spreads out, about 15 to 20 meters apart, so one bomb can't hit two people.
In the last 30 seconds, don't get greedy for kills. You can't kill all the enemies. When you see the shuttle coming, run for the door. Getting on the shuttle counts as mission complete—dying at the door is still a failure.
I've seen many new players jump straight to difficulty 8 or 9, then spend the whole mission lying on the ground waiting to be revived.
I suggest starting at difficulty 5. Enemy density at 5 is similar to 7, but there are fewer heavy armored units. You have enough time to practice aiming and movement. Once you can consistently avoid going down at 5, then move up.
Difficulty 7 is a threshold. Starting at 7, heavy armor spawns much more frequently, and your damage output must be able to handle them. If your playstyle suddenly stops working at 7, go back and look at your loadout—you're probably missing anti-armor capability.
Difficulty 9 requires high coordination, and random squads fail more than half the time. Not saying you can't do 9, but you have to accept frequent failures. Personally, I think difficulty 7 has the best reward-to-difficulty ratio, and the sample farming efficiency is good enough.
Higher armor value isn't always better in this game—getting hit reduces your movement speed. I like wearing light armor against bugs. The survival benefit from mobility is greater than tanking hits.
When you run out of ammo, don't immediately call for resupply. Check the ground for ammo boxes dropped by dead teammates.
When you hear robot gunships, find cover immediately. Don't stand there trading shots with them.
Bug holes and robot factories can be destroyed by throwing a hellbomb directly inside. You don't have to slowly clear the small enemies before blowing up the core.
I've been playing this game for over a year and still log on a few times a week. Every balance update invalidates some strategies and creates new loadout ideas.
People are constantly discussing these on the Helldivers subreddit and several Discord servers. Check them out if you're interested.