So I might have actually worked it out. They were still slow, yes, and I never actually saw what happened once it had finished downloading; but when it was about 95% of the bar, I went to cook dinner and when I came back after maybe 20 minutes everything was completed and there was an error on the screen. All but one of the games had been downloaded successfully.
My thoughts are that the download queue is either sort of a fallacy, or it was broken for me. I reckon it was downloading everything at once and the one game that got flagged up for potential virus content caused the entire thing to grind to a halt. Either way, they're done now. That said, I'd like to help just in case it was an actual issue; the game that was being downloaded (as in the one that was listed as active, I had about 19 games queued up) was Starship Inanna, the next couple were Odd Realm and Luckless Seven. The game that errored for potential malware was Sexperiment. The opening line of the butler debug error is:
Open D:\[path]\Sexperiment v0.4.exe: Operation did not complete successfully because the file contains a virus or potentially unwanted software.
The rest has apparently been sent to the team automatically. I'd copy in the entire stack trace or event log, but I can't copy and paste from it, nor is there an option to just open a .txt of the report for me to upload or link.