How about a new idea for DnD Next? If a fighter gets to crit on a 20, why not love for the wizard who throws a fireball. I don’t think this should be a feat, but I think this should be a standard rule.
Spells Criticals
When the target of a spells that has a save effect critically fails the save (rolls a natural 1), the target takes the maximum damage of the spell plus an additional roll of all damage dice.
Thoughts?
Throat Punch Games 