Just been testing speeds, managed Processing rate of 265 MB/s and Throughput (All time) of 395.3 MB/s. This is with the tape drive physically attached to the backup server.
Backed up a 971.9 GB VM to tape (From the Disk backup) in 1hr and 3 mins. I'm very impressed with the tape drive and Veeam. This was using LTO7, with LTO6 it took 1hr 40 mins.