Interesting data, see page 9 of this document,
https://www.uscis.gov/sites/default...1B_RFE_Completions_Data_-_FY2015-FY2019Q2.pdf
For I-129 submitted by mail to USCIS for TN status
FY2015, 95.1% initial approved, 74.8% approved after RFE
FY2016, 90.7% initial approved, 64.2% approved after RFE
FY2017, 91.6% initial approved, 64.7% approved after RFE
FY2018, 88.2% initial approved, 59.9% approved after RFE
FY2019, 88.4% initial approved, 57.6% approved after RFE (Oct'18 to March'19, FY2019 so far)
Although the trend is going down, it is not that bad. If you have a strong petition, meeting all the criteria of TN status, you will get approved by mail with form I-129
https://www.uscis.gov/sites/default...1B_RFE_Completions_Data_-_FY2015-FY2019Q2.pdf
For I-129 submitted by mail to USCIS for TN status
FY2015, 95.1% initial approved, 74.8% approved after RFE
FY2016, 90.7% initial approved, 64.2% approved after RFE
FY2017, 91.6% initial approved, 64.7% approved after RFE
FY2018, 88.2% initial approved, 59.9% approved after RFE
FY2019, 88.4% initial approved, 57.6% approved after RFE (Oct'18 to March'19, FY2019 so far)
Although the trend is going down, it is not that bad. If you have a strong petition, meeting all the criteria of TN status, you will get approved by mail with form I-129