but let's be honest, mages will still rule. mages roll more dice, their damage therefore ranges based on rolling lots of high dice.
4d10 (level 17 firebolt) can roll 40damage 2d8+10 from some martial hitting twice is only 26. The 'big' damage lucky roll is already built into spells. So in terms of surprising dmg rolls, you'll still get the big feels from spells.
not to mention most are multi target. Also most caster spells never crit anyway. So I'm not sure its going to deter them.