As of right now, it's downloading really fast. Yesterday it was so slow... download speeds is so random with Bitcoin Core for some reason.
Maybe HDD access is the bottleneck? My mainnet sync speed varied by a factor of 10, likely due to Core's inefficient memory caching.
But why would the speed be random due using HDD? according to the network activity, it just stops downloading, there are huge gaps of no activity in the network window, I mean you get these big green lines when it goes fast, then it just stops download, then it begins again, at lower speeds, eventually the speed is so slow that it's maddening so I have to close it and re-open again.
Next time I sync a full blockchain I will use SSD, but like I said... it just has big gaps in between downloading, then download speed decreases.