That is only if you are playing a pure barbarian. And that extra damage is ONLY on a vorpal (20) roll. The extra damage on a vorpal and an extra 25 melee power on a pure Barb is still not going to match a Paladin in terms of DPS. Especially since the FB tree itself ability-wise, for the most part garbage.
Occult Slayer gets from a pure Barb 20 MRR while the Ravager gets nothing in terms of passive bonus in the trees ( I suggest PRR).