IRCC do not publish any official data on how different nationalities being treated. Only data points come from the people in a forum like here who complained about the delay.
Also, IRCC minister denied any extensive delay in processing Iranian PR applications. After media attention to the case, he came clean and said this:
"These efforts have shown a marked improvement on the overall processing times for Iranian permanent resident applications. Notably, in 2015 the average wait time for Iranian permanent resident applications was 32.6 months longer than for citizens of all other countries. By July, the difference was down to 10.5 months."
Discrimination means someone is treated differently (in negative manner) with no reason (At least the way I think it is).