One reason I like the 1d5 on the crit hit table is that otherwise those results tend to not show up at all. Okay, at least in Deathwatch. Opponents would generally go from 5-6 wounds to -11 in a single blow, so the critical hit tables didn't see much use. Now when we're fighting a big bad, they can occasionally suffer from Fatigue or such, which is a nice change. But that's Deathwatch, where starting damage from a chainsword can be 1d10+15 pen4.
I know several people who toss out the "Confirm Righteous Fury" rolls altogether. Not a big deal.