Consistancy, Not Exceptions.
I think that Barbarians should follow the rules and have a D10 like everyone else.
...to make up for the loss of HP and to discourage Barbarians from using Charisma as a dump stat they would get a new class feature:
Imposing (Ex)
A barbarian's presence and personal intensity is tied closely to their hulking size and stamina. Barbarians may add their CHA Modifier, as well as the normal CON modifier, to their Hit Die for determining Hit Points.
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Thoughts?