Backupexec is a single threaded product, even more so that build. No multi-plexing, no multi-streaming, no multi-core advantages, etc....
You could have a 10000Gbps backbone haul and still not be able to utilize the available bandwidth.
The neat thing about backup is that it shows your weakest link in your environment. Well it doesn't really show you what is that weak link, but you'll only go as fast as capable. So you need to verify the source can read that fast. You need to make sure your target can write that fast. You will need more concurrent streams to start to saturate the links. You will need to write your backups to fast disk, etc... This kind of testing is tedious. And using an aging product as BE2010 is not helping either. This was one of the worst builds since it introduced so much new technology. Make sure you are installed to the latest R3 or greater, and all the hotfixes, and you'll need to redeploy agents too in most cases.
Few folks can come close to saturating a single 1GbE link, averaging around 40-80MB/s. If you're getting around 80, you're in good company, and "normal," for most of the hundreds of installs I've worked on.
To get higher, you need to do a lot of tuning, but more importantly, you need to have a fast B2D target.
Good luck.