aramis erak
Legend
Fumbles are a good balance if you allow critical hits.
Not really.
The critical hit is merely a 2-for-1 in the RAW. It needs no balance, really. Any anything worse than disadvantage for one attack (not one round) is overbalancing the other direction.
Plus, for those with simulationist leanings, they are a big problem, as the rate of anything that most RPGers would consider a fumble (dropped weapon, etc) are FAR far less frequent than even 1/2400 person-seconds or 1/400 person-rounds (1/20 nat 1, 1/20 confirm fumble, 6 seconds)... and that's still too many for real applied combat-skills.