Len said:
However, it's not supposed to be balanced all by itself - it's supposed to be worth one feat. It's not a freebie.
But it's worth far more than one feat, IMO, and the trade-off doesn't nearly cover the overhead of power this grants.
Compare it to Power Attack. Power Attack gives you the same damage bonus (more if you use a two-handed weapon, less if you're a rogue with less BAB), but has a more significant penalty (the penalty applies just as often as the bonus).
Exactly. Also, you cannot avoid that penalty at all, as you inevetibly incur the penalty when you attempt to get the bonus (you have to sacrifice some of your attack bonus in order to get the damage bonus, and then you might miss, giving up the bonus for nothing).
The fear penalty, on the other hand, can occur, but it doesn't have to. You might go for weeks without encountering any fear effect, but you get the bonus all the time.
Also, Craven can only be used when you're sneak attacking, which limits it.
Especially for a rogue, it's not that much of a limit. They're limited to sneak attacks to begin with. The limit is there for those who take one level of rogue, though.
Still, I say it's too much. It's, statistically seen, almost 6 extra dice of SA at level 20 (6d6 is 21 on average.). I've seen feats that grant you one extra die. Two or even three might be okay (this would be +10 damage) with a drawback, but this is too much.