I use backblaze for my backups with restic and enjoy it, but their service is just so slow I'm now looking at giving digitalocean a try instead. Transfers both up and down are painfully slow even on a 1Gbit connection.
Have you tried enabling more threads (add -o b2.connections=$number)? It improved enough to make it ok for my (admittedly tiny) backup needs. The process of creating a new snapshot is still really slow though, but I'm not sure that is B2's fault.
I'll give this a go thanks
Where do you connect from? Backblaze only has one datacenter, in Sacramento, CA [1].