I'm not too surprised with these results. My 7850 defaults to 180Mhz on the 3.8-3.10 kernels, but runs at 860Mhz on 3.11 with the new dynamic power management code. There is a similar gap in memory speeds as well.
Once there are tests running on that newer kernel, the results should improve somewhat. There's definitely still work to do, but the gap should shrink a bit.