I agree I'd expect somewhat lower than Adreno 320 performance. The Adreno 405 is not used in high-end SoCs so it doesn't really make sense that it would be all that fast - that's what the 420 is for.
That said, there's roughly a factor 2 in graphics performance between slowest adreno 320 and fastest adreno 320 if you hunt for benchmarks. And the choice of memory (lpddr2 vs lpddr3) seems to make a much bigger impact than clocks there (of course, there's other factors too). I would certainly expect the Snapdragon 610 to ship with lpddr3 (even though it still seems to support lpddr2), so I'd not be surprised if it can beat at least the slower adreno 320 devices neither.
