My own rough calculation is that a single 14 bit image from a D7100 is 42.8Mbytes, so that would indicate that within 5 shots, (published buffer size), the card would be writing about 1 image per second, assuming wire speed processing through the ASIC architecture of the expeed processor.
If the D7100 supports UHS-104, it would about double the performance once the buffer is full to around 2 frames per second.
Finally, the real cure appears to be UHS-II, at 312Mbytes/sec, (again, if the ASIC processes that fast). I can't find any card like that yet, hopefully it will be out soon.
Edit to add - I am guessing the D7100 does not support the speed of UHS-II. I found that in the teardown of the D600, it uses a chip for the SD interface that is UHS-1 only...
I am guessing the D7100 shares a near identical chipset as the D600.
Some bad news - reading the chart for the TE4302 chip, it runs at the 100mhz speed, so at least for the D600, it is a waste of money to buy the UHS-104 spec cards. Again, I am guessing that will be the story for the D7100.
"Extraordinary claims require extraordinary proof " - Carl Sagan