For those who has passed 6-month mark and want to do something about it, here is an idea.
First, go to the link below to find your member of parliament:
http://www.lop.parl.gc.ca/ParlInfo/Compilations/HouseOfCommons/MemberByPostalCode.aspx?Menu=HOC
Second, write a short letter describing your situation. If not sure how to write a letter, google 'how to write a letter to your member of parliament canada'.
What you can talk about:
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Dear Mr/Mrs MP NAME,
I have lived in Canada past XXX years. I have been contributing to Canadian economy since XXXX as skilled worker on a work permit. Recently, upon my application, my province nominated me to become a permanent resident through Express Entry. As this stream promises priority processing of applications, It has been my understanding that CIC would allocate adequate number of personnel to ensure reasonable processing times.
However, through several channels of information, I observed that other streams of Express Entry, such as CEC and FSW, have been consistently processed twice as fast as PNP stream. While I don't think CIC is deliberately delaying PNP applications, I wanted to bring a possible work distribution issue to your attention.
Best Regards,
XYZ