QFT
We derailed this for a long time (although the discussion was valuable IMO). And, the OP has probably gone on with a leveling scheme by now.
But, the original question has to do with a viable rogue/barbarian. Based on the discussions that is at least 14 levels of barbarian if you make that your primary class or 12 levels of rogue (remember the OP's initial desire to use acrobat enhancements).
So, I'm going to go with my earlier advice which started the derailment. If you are looking to be the aggro magnet go with the barbarian as your main class. If you are looking to avoid that and get most of your DPS from the backstab bonus go the rogue route.
A barbarian/rogue 14/2 split has a BAB of 15 (the progression is 15/15/20/25/25). A rogue/barbarian 12/4 split has a BAB of 13 (the progression is 13/13/18/23). As I noted, there isn't much you gain from a split like this -- a rogue 16 has a BAB of 12 (the progression is 12/12/17/22) and for that extra +1 on each swing you are giving up 2d6 of backstab damage.
Bottom line here is that the barbarian is going to do more damage (as we have discovered, because things between the two won't be equal) and so will draw more aggro from mobs. If that is what the OP is looking for then he should go the barbarian route. If not, he should probably just go pure rogue (or at most go for a 15/1 split for the minimal impact of L1 rages). Since people like to spam rage I'm not sure if there really is going to be much difference in damage output for the 15/1 split as opposed to the straight 16 rogue.