I think you're talking about the Snapdragon 808 which your phone has. That's a big.LITTLE CPU which means that it's meant to use the 4 little cores almost all of the time and use the big cores only when high performance is really required. What I mean to say is that the 4+2/4+4/4+4+4 configurations aren't meant to parallelize across all cores but rather to minimize power consumption.