I am using Microsoft Remote Desktop v. 8.0.36 (have also tried 8.0.33) to a windows server. When I use the button to the left of 1 on my keyboard, I get a backslash in the remote desktop. If I enable the on-screen keyboard, I can see that it is supposed give the backtick, and if I click on the on-screen keyboard, I also get the backtick as expected.
I have a US style keyboard and I am using El Capitan. I have also used the old Microsoft RDC program (v. 2.1.1 from 2011). Here it works fine and same with Cord. The problem is that the 2011 RDC crashes on avg. once per hour, which gets frustrating and Cord does the same for random reasons (certain local shortcuts tend to crash it).
I have seen that earlier (pre 8.0.15), there was a bug so that it was impossible to get a backslash. Now there just seems to be to many backslashes.