Space Marine 2 gives you a health bar you cannot heal and an armour bar you refill constantly. Everything about how the game plays follows from that split.
Armour comes back from violence. Land a perfect parry and the follow-up Gun Strike restores a segment. Execute a staggered enemy and you get more. Bulwark plants a banner and refills it for the whole squad. Health comes back from stimpacks, and there are never enough.
So a build in Operations is really an answer to one question: what is your armour engine, and does it work when forty Tyranids are on top of you?
Parry, dodge, and the colour that decides which
Attacks flash before they land. Blue can be parried. Red cannot, and must be dodged.
That is the entire defensive game, and players who try to dodge everything spend the whole mission with no armour, because dodging gives you nothing back. Parrying does.
The Gun Strike that follows a parry is not a bonus. It is your resource economy, and a class that cannot parry reliably is a class that runs on stimpacks it does not have.
Contested health, the grey portion of the bar after you take a hit, comes back if you kill something quickly. Backing off to be safe throws it away. The game is rewarding aggression at the exact moment your instincts say retreat.
The six classes and what each one is actually for
Tactical is the generalist and the best pick for a first hundred hours. Auspex Scan marks a target and multiplies incoming damage against it, which makes Tactical the answer to any Extremis enemy the team is struggling with.
Bulwark carries the banner, has no ranged weapon worth the name, and keeps the squad alive. The most valuable class in a random group and the least flashy.
Assault jumps into the middle and hammers down. Enormous fun, highest death rate, and genuinely strong once you understand that the jump pack is a defensive tool as much as an offensive one.
Vanguard grapples to a target and closes distance instantly. It restores armour on the grapple, which gives it the most aggressive armour engine in the game and the least margin if you pick the wrong target.
Sniper has cloak, which is a full reset button, and struggles with hordes. Best against Extremis and Terminus targets, worst when the screen fills.
Heavy is a stationary gun platform with an iron halo. Enormous damage output against everything, no melee to speak of, and completely dependent on the team keeping things off it.
Perks are a small number of large decisions
Each class has perk tiers unlocked by class level, and unlike most games the perks meaningfully change how the class plays rather than adding percentages.
The pattern worth following: take the perks that improve your armour restoration first, damage second. A Vanguard that restores more armour on grapple can grapple more often, which is more damage than a damage perk gives you.
Team perks, the ones that benefit the squad, are undervalued in matchmaking because you never see the numbers. Take them anyway.
Weapons, mastery, and Armoury Data
Weapons level through use and unlock mastery perks. Upgrading a weapon's tier requires Armoury Data, which is limited and earned from higher difficulties.
That creates the standard trap: spreading Armoury Data across six weapons you like leaves you with six mid-tier weapons and nothing that performs on Ruthless. Pick two, take them to the top, then branch.
Melta weapons deserve a specific mention. They are absurd against hordes at close range and nearly useless past it, which fits Bulwark and Assault exactly.
Difficulty is where the build stops being optional
Up to Substantial you can play more or less anything. Ruthless and above, the Extremis enemies stop being interruptions and start being the encounter.
Zoanthropes float and shield each other, which is a problem no melee class solves alone. Lictors pull a player away from the group. Neurothropes buff everything nearby.
This is why a squad of three melee classes fails on Lethal regardless of individual skill. Somebody needs a reliable answer to a shielded floating target, and the composition question outranks the build question.
The Space Marine 2 walkthrough covers the campaign; Operations is where the builds matter.
