they do, because the spells aren't scaling based on weapon damage
there's also... a huge disadvantage to not running a hybrid build
due to the way the resource system works
for example, running a pistol + a catalyst (ranger/caster hybrid) lets you use ranged attacks to generate willpower, and then spells to convert the willpower back into rage, creating a back and forth loop for constantly doing damage
but there's also uniques (and very rare magic rolls) that allow you to cast spells or use attacks without having to run the hybrid setup
for example, a 2h sword that adds lighitning damage to attacks and spells and lets you cast lightning spells
or a shield that lets you cast sacred spells
i htink the game has a lot of promise, but, in it's current state it's very... basic
there's things like two abilites basically fulfililng the same role, but one does 20x the damage so you'd never use the other
and... casters aren't totally broken, they just don't scale into deep endgame yet. the hotfix they announced today looks like it might address that