how about changing hp rolls from 50%-100% of the hit dice to 75%-100% of the hit dice (similar to how cure light wounds would heal for a minimum of 4 from dice roll). That way you would still have randomized hp, i.e. characters still aren't identical mechanically but you also wouldn't have some classes outscaled entirely like barbs.
what i'm suggesting is:
barb hp rolls 9-12 from 6-12
fighter/paladin/ranger hp rolls 7 or 8-10 from 5-10
cleric/druid hp rolls 6-8 from 4-8
rogue/bard hp rolls 4 or 5-6 from 3-6
wizard/sorcerer hp rolls 3-4 from 2-4
what i'm suggesting is:
barb hp rolls 9-12 from 6-12
fighter/paladin/ranger hp rolls 7 or 8-10 from 5-10
cleric/druid hp rolls 6-8 from 4-8
rogue/bard hp rolls 4 or 5-6 from 3-6
wizard/sorcerer hp rolls 3-4 from 2-4