Okay so I did some research on it, and it turns out theres no crit cap for spells.

Only melee will hit a cap on how much crit will help them since they have to work it up against mitigration and misses.

So it's stack on that crit, as long as you hit the 16% spell hit, balance on +dmg and +crit. mods like Dr.Damage helps a good bit with balancing stats ingame.