TFA author. How does the word "dispatching" hint at the order of magnitude of anything? What orders of magnitude do depend on is your competition. Outdoing a CPU at operation X is easier than outdoing a GPU at X [assuming the GPU does X reasonably well] which is easier than outdoing a DSP at X [assuming the DSP does X reasonably well]. If your competition is reasonably optimized programmable accelerators, your opportunities to beat it start shrinking.
Source: my day job