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 · Pure Optimization
The genre-defining loot ARPG whose builds, runes, and trade economy players still optimize decades later.

Optimization · Pure Optimization
A breezy dungeon-crawling loot game about builds and ever-better randomized gear.
Diablo II leans Optimization (Pure Optimization); Torchlight 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 II
Positioning and potion reflexes, little else physical
Torchlight
Click-to-kill combat with minimal mechanical demand
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Diablo II
Monster AI is fully mappable
Torchlight
Solo dungeon crawl, no adaptive opposition
Diablo II leans a little harder on variance, though the gap is small.
Diablo II
Loot RNG and random maps drive the grind
Torchlight
Randomized loot and dungeon layouts gate power
Diablo II leans a little harder on optimization, though the gap is small.
Diablo II
Builds, breakpoints, rune economy, magic-find routing are the game
Torchlight
Build paths and gear stats are the real game
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.