I'm also experiencing horrendous backup speeds via the QNAP IDrive backup application. It is averaging approx 460MB an hour and has been running over 48 hours and is consistently slow. I cannot confirm how long this has been going on for as I have only recently put a large amount of data to be included in the backup profile and have noticed how long it is taking,
As other members have mentioned, I have ran the same backup profile but using Google Drive and was getting 4.5GB an hour. I'm based in the UK and appreciate I would not get the same sort of speeds but not as slow as this. My connection has an upstream of 12Mb and it is currently connected to via HTTPS to 66.51.30.102, average echo response is 182ms. My ISP does not traffic shape based on the package I am on and the backup has been running overnight when I would expect my ISP's local infrastructure to be under utilised, so that factor can be ignored also.
There is nothing wrong with the upstream connection as Google Drive is utilising it correctly, there are no issues with the QNAP or the drives within it as I ran the Google Drive test via Cloud Drive Sync which is a QNAP application similar to the IDrive.
For your reference, the model is QNAP 419P+