To my knowledge, currently all abilities, including things like heavy attacks, scale off your highest offensive stat. Regardless whether that stat is Spell Damage, or Weapon Damage.

I think that these split categories of "Spell Damage" and "Weapon Damage" as well as "Spell Critical" and "Weapon Critical" should be removed and just replaced with "Damage" and "Critical". Below are a few bullet points with reasoning.

Why the current system feels outdated:

• Many skills in the game currently read quite awkwardly. Such as "Gain Major Savagery and Major Prophecy, increasing your..." or "Gain Major Brutality and Major Sorcery..." I think every buff skill in the game provides increases to both Weapon and Spell damage and crit stats. So it feels redundant and needlessly long winded to have them separated at all.
• The same awkward 'clunkiness' applies to many set bonuses, "Gain 129 Weapon damage and 129 spell damage". Again, I think every single set that has a damage component applies it to both spell and weapon damage, so why bother splitting into 2 things?
• For newer players, if they aren't aware that everything scales with your highest stat, it may be confusing for them. For example, if they are trying to increase their Heavy Attack damage with a 2-H but they won't intuitively know that this can also scale with Spell damage as well as Weapon Damage.

I think that merging "Spell" and "Weapon" damage and critical stats into single "Damage" and "Critical" stats would:

• Make the game more intuitive and easier to understand for newer players.
• Reduce tooltip bloat on skills and set item bonuses.
• Generally make the game feel cleaner, tighter, and more polished.