I'm looking at the aberrant bloodline and there's some things I find strange.
At level 8, you're immune to sickened and nauseated while raging. There's also a rage power (internal fortitude) that does the same thing. Is there any reason not to trade this out through Primalist and get it through the rage power while picking up an extra one to boot?
How does rage cycling work with this ability? I've seen people take a flawed scarlet and green ioun stone to turn the fatigue into sickness, but once you drop out of rage you're no longer immune to sickness. Does becoming immune by going back into rage clear any sickness effects on you? Does that mean at the end of the battle, when you stop raging, you're going to be stuck with a few rounds of sickness? (not a big deal I know, but just want to make sure)
In short:
No, there's no reason not to trade out the 8th level bloodline power for two rage powers via primalist (unless you're playing in PFS or another game which has banned primalist).
Yes, going back into rage clears any sickened effect, but doesn't stop you from becoming sickened yet again as soon as you're not raging anymore.
Yes, you'll be sickened for a few rounds after ending a rage. Note that since the internal fort/green cabochon ioun combo allows you to cycle every round, you'll rarely, if ever, actually end combat having raged for more than a round.
Thank you for the answers.
With that in mind, is it worth keeping any of the aberrant abilities besides reach? One rage power and an ioun stone covers sickened, nauseated, fatigue and exhaustion and I'm not sure I'd pick immunity to staggered over two rage powers. (Is it even worth aberrant at all? I really like the flavour but if I'm going to trade away all but one power it feels a bit pointless...)
Well, it very much depends on what your mechanical overall goals are and whether those benefit from staying a mostly single-classed bloodrager. The same goes for the value of rage-cycling, which for a higher level bloodrager normally has a high cost (less use/more castings of spells via greater bloodrage) and little benefit.
Personally I find aberrant more suitable for 4-level dips with melee control builds looking to maximize reach, notably since that also grants enough rounds of bloodrage (typically at the very least 12) for an adventuring day. Or possibly getting 12 levels and trading out both the 8th and 12th level bloodline powers for Superstition and Come and Get Me, which is a very good base to pimp out with two more rage powers, spells, items and feats for great AoO control/defense and debuffing power.
Regarding rage-cycling, I think it's generally only worth investing in if also getting Spell Sunder. And in such a case I still wouldn't bother with Internal Fort until 12th level.
I think the bloodrager class otherwise is mechanically more suitable for durable damage-focused builds. Which, much depending on party and preferences, typically makes abyssal, destined, draconic or especially arcane stronger bloodlines than aberrant IME.
And regarding flavor, I'd ask your DM to let you tweak the flavor of whatever bloodline and other components you choose so they fit with your character idea. In the case of bloodrager bloodline powers, I think many of them would work perfect as they are with an aberrant flavor, and many would only require a minor mechanical tweak, such as changing the fire damage dealt by the claws of abyssal to acid.
If you really wanna pump the aberrant flavor, I suggest you dip a level or two into ragechemist/vivisectionist alchemist for rage mutagen, a little bit of sneak attack and especially a grabbing tentacle or two via discovery and the Extra Discovery feat. Which is most probably also great from a purely mechanical point of view.
And if you really wanna go over-the-top aberrant bloodrager, ask your DM for permission to use my Wrathblood home brew archetype. Just make sure both you and your DM carefully reads through the mechanical goals of the archetype and are aware that your bloodrager can be much more versatile both in and outside of combat, more like a magus or other 6/9 caster class (despite not having any spells at all).
Well, you do get a nice suite of defenses from the abilities after 8th.
level 12 gives 50% chance to ignore critical hits? That is the same as moderate fortification, a +3 armor property. That could be useful. Obviously you would want to retrain it out if you ever get to level 20.
Level 16 gives you immunity...to a rather nice number of abilities that could do some serious damage.
Level 20... well, it makes level 12 useless, since you are now immune to crits (and this is constant, not raging). And you also get blindsight (a rather nice ability) and more DR (who doesn't love that?)