Natural attacks are not bound by BAB's limitation on number of attacks.
At BAB of 6+, the bloodrager using only those claws has 2 claw attacks.
At BAB of <6, the bloodrager using only those claws has 2 claw attacks.
I guess I'm not sure where the confusion lies.
The only place in the game where you can get iteratives with natural attacks is if you're a druid's animal companion with the multi-attack ability. Chances are that if you're a bloodrager, you aren't a druid's animal companion.
Before I begin, let's visit Natural Attack rules found in the Core Rulebook.
Page 182: "You do not receive additional natural attacks for a high base attack bonus. Instead, you receive additional attack rolls for multiple limb and body parts capable of making the attack (as noted by the race or ability that grants the attacks). If you possess only one natural attack (such as a bite—two claw attacks do not qualify), you add 1–1/2 times your Strength bonus on damage rolls made with that attack." (this is also found in the PRD at http://paizo.com/prd/combat.html)
What this means is the following. At BaB of 1, a creature with natural attacks will only get one attack per round. At BaB of 6, if the creature has multiple limbs capable of completely natural attacks, it will get two natural attacks per round. The first limb is at BaB of 6, the second limb is at BaB of 1. Each increase of BaB by 6 increases the number of limbs that can be attacked with.
Umm, no. That's not what it means. At any BAB a creature with natural attacks can take ALL of their normal natural attacks as a full round attack.
Two-weapon fighting does not apply to natural attacks. For the purposes of a second attack, the second limb capable of performing a natural attack is not an "off-hand". There is no default negative to be changed on a second attack for offhand, because there is no off hand.
True, two-weapon fighting is for manufactured weapons...
Having no offhand also means that Power Attack can be used with every natural attack the creature has.
Regardless of whether you are using an offhand or not, Power Attack would affect every attack you make on a turn if you activate the ability. It adds less damage to an offhand attack, but still has the penalty to attack.
Now, let's look at the Bloodrager Bloodline Abyssal. Page 11 of Advanced Class Playtest.
"Claws (Su): At 1st level, you grow claws. These claws are
treated as natural weapons, allowing you to make two
claw attacks as a full-attack action using your full base
attack bonus"This sentence makes absolutely no...
Actually, this is just restating the normal natural weapons rules...
Peptic, your understanding of how natural attacks and BAB interact is incorrect, as Cheapy and Snig have pointed out.
Natural attacks are powerful.
The barbarian can use natural weapons and power attack, too. If he's from a race that gets an arcane spell-like ability he can even use arcane strike.
If the barbarian doesn't have natural attacks he can take rage powers to get them. At level 4 he can have a bite and two claws while raging.
Really the auto enlarge self on rage is the only thing the barbarian can't do. But he can do lots of other things instead.
Seems over powered at lower levels. At level 6, it has a good chance of killing a level 6 PC in one round. A standard CR 6 monster will die in less than 3, probability two. That's even if the Bloodrager is the only one attacking.
That's pretty much what a druid does already.
Or an archer.
Or a full attacking monk.
Or an Eidolon.
Or heck my paladin was doing pretty scary damage at level 6.
Point being is that a level 6 full bab class focused on killing is pretty much going to be good at killing. Crushing a CR6 critter in a slug fest is par for the course.
Yep.
Quick! Let's limit the bloodrager to a maximum damage of D8+4! Per round!
Okay, enough sarcasm. A warrior type should be able to hit about as hard as the bloodrager of your example does. It's one of the few upsides to a Full BAB-class.
As mentioned above, the barbarian rage power Lesser Beast Totem is already exactly as powerful as the abyssal claws.
It is also true that at lower levels, two natural attack claws do more (basic) damage than any weapon combo (2-hander, 2 weapons, etc.). Some barbarians don't even wield a weapon at levels 2-5, if they have Rage left. At level 6 and beyond, Full Attack with a 2-hander is usually a better option.