You cant have your cake and eat it, at two threads it will throttle the frequency , the ST score is valid only with a single core active and the other idling, you wont have twice the ST perf when there s 2 threads, let alone 3.
Nothing in this power range, it s typicaly a 12-15W chip that had been squeezed into power devices wich it s actualy not meant for, or rather there s some technical limitations that retain it from performing as well, in respect of the competitions, as its more power hungry siblings, or simply compared to itself but at say 15W.
First limitation is that the CPU part is over the point at wich IPC delta/power delta is still greater or equal to 1 in the current state of the uarches, it is below 1 since SB at least in Intel uarch, so lower IPC designs like BT or Mullins/Beema have no trouble being on par perf/watt wise despite being one and two nodes late respectively, at equal nodes it would be a slaughter.
Second limitation is the poor perf/watt of Intel s GPU, this is an area that is not compensated by the 14-16nm node.
Lastly, their current process does not seem to be up to their own expectations, if any indication the current chips are surely cherry picked and this is telling about the dispersions they must have in their process, with yields surely in the low double digit, something like 20-25%.