TallIan
Explorer
The balance is not against how many times you roll an attack, but against the same probability of getting a critical hit. Your wizard only had a 1 in 20 chance of getting a critical hit, and should have had a similar chance of a critical miss (or the minimal hit option I proposed). The fighters had a TON of chances for a critical hit, but without a counterbalance, they just did better overall because of the chance for extra damage with no drawback (depending on the argument of the value of saves vs. AC)
Something you (and others) seem to have in mind is for critical misses to be catastrophic in nature, and the rest of my post argued against this. The negative for a critical miss should not in any way be significantly worse than the benefit of a critical hit (thus my minimal hit suggestion instead). If you want to have catastrophic critical misses, the chance of those must be MUCH lower than 5%; I would suggest only having them happen when the roll has either advantage or disadvantage and BOTH dice roll 1. This would make regular attacks unable to critically miss, and even advantage/disadvantage attacks only have a 1/400 chance of happening. While this might happen occasionally in a campaign (creating the memorable moments), it shouldn't significantly impact even the attackiest of fighters since they're still getting all those critical hits.
I still disagree that they critical hits should be balanced off against critical failures - no matter how balanced tehy are against each other. Critical hits make martial characters more deadly (it increases their damage) conversely critical failures make martial characters less deadly. So if you have a magic system that is more powerful than the martial system in the game, adding critical hits without adding critical failures can improve the magic-martial balance.