head to head
Neither is simply harder - they are hard in different places. Baldur's Gate 3 demands more reads; Diablo IV demands more execution.

Optimization · Systems & Chaos
A D&D CRPG where build optimization and dice variance dominate every encounter.

Optimization · Systems & Chaos
An ARPG loot grind about chasing affix rolls to feed a damage-stack build.
Baldur's Gate 3 leans Optimization (Systems & Chaos); Diablo IV leans Optimization (Systems & Chaos).
Diablo IV leans clearly harder on execution.
Baldur's Gate 3
Turn-based; no input dexterity.
Diablo IV
Clicking and dodging are light; gear carries you.
Baldur's Gate 3 leans clearly harder on reads.
Baldur's Gate 3
Companions/enemies scripted, not adaptive to player modeling.
Diablo IV
Enemies and bosses are scripted; no adaptive opponent.
Baldur's Gate 3 leans a little harder on variance, though the gap is small.
Baldur's Gate 3
Dice rolls, hidden checks, encounter RNG everywhere.
Diablo IV
Loot rolls, affixes, and uniques drive every session.
Baldur's Gate 3 leans a little harder on optimization, though the gap is small.
Baldur's Gate 3
Builds, party comp, action economy fully solvable.
Diablo IV
Paragon, aspects, and damage buckets are solvable theorycraft.
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.