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

Optimization · Systems & Chaos
An ARPG loot grind about chasing affix rolls to feed a damage-stack build.

Optimization · Pure Optimization
A colorful loot ARPG where theorycrafting builds beats anything your hands do.
Diablo IV leans Optimization (Systems & Chaos); Torchlight II leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo IV
Clicking and dodging are light; gear carries you.
Torchlight II
Faster combat asks for dodging and skill timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo IV
Enemies and bosses are scripted; no adaptive opponent.
Torchlight II
Enemies are scripted swarms, never adaptive
Diablo IV leans a little harder on variance, though the gap is small.
Diablo IV
Loot rolls, affixes, and uniques drive every session.
Torchlight II
Loot rolls and random maps drive the chase
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo IV
Paragon, aspects, and damage buckets are solvable theorycraft.
Torchlight II
Skill trees and gear synergies decide character power
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.