head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Optimization · Pure Optimization
A pure loot-and-build treadmill where set-bonus optimisation and Rift pushing define performance.

Optimization · Pure Optimization
A third-person roguelike where item snowballs outscale the difficulty timer.
Diablo III leans Optimization (Pure Optimization); Risk of Rain 2 leans Optimization (Pure Optimization).
Risk of Rain 2 leans a little harder on execution, though the gap is small.
Diablo III
Greater Rift pushing has minor mechanical demand in builds
Risk of Rain 2
Aim and movement matter under escalating swarm pressure.
Diablo III leans a little harder on reads, though the gap is small.
Diablo III
No meaningful adaptive opponent; co-op is cooperative
Risk of Rain 2
Enemies follow fixed AI; no opponent models you.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo III
Primal Ancient drops and set dungeon RNG drive the grind
Risk of Rain 2
Item drops and stage selection randomized each run.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo III
Set bonuses and paragon levelling are almost entirely solvable
Risk of Rain 2
Item stacking and scaling routes dominate run outcomes.
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.