Uh. 80% to 50%. That's how percentages work.
It only takes about 7 swings to get 14d6 out of 1d12 per swing (approximately speaking). So at a ratio of 7 swings per spell cast the barbarian is doing +80% to your +50%. Of course he can keep on doing it forever and you'll eventually run out of spell points.
So, how is that irrelevant?
Uh. Spell crits? We're comparing to melee right? You realize they get "crits" without having to take any enhancements, right?