I actually switched to OneDrive when Dropbox changed their pricing a while ago. Microsoft's offering was way more competitive on both price (€100/yr for 5x1TB) and features (Office access and integration, etc.)
As soon as I noticed this issue, the deal of 1TB storage with a O365 subscription also went sour. 1TB I can't really use -- no deal.
This problem is well known; it's all over the internet -- OneDrive is a sloth. It doesn't affect downloads, btw.