Hello Ross,
To resolve slow throughput issue take a lot at the following technotes.
1. Reasons why the data throughput rate can be slower than the theoretical maximum when backing up to tape media
http://support.veritas.com/docs/231488
2.How to correct slow backup performance, slow virus or pre-job scans, and agent initialization problems on fragmented Windows NT, Windows 2000, and Windows 2003 server partitions
http://support.veritas.com/docs/237444
3. Remote backups performed using agents (Agent for SQL, Agent for Exchange, Remote Agent, etc.) are unresponsive or extremely slow on particular machines.
http://support.veritas.com/docs/190828
4.What Backup Exec settings can be modified to reduce the amount of time it takes for a backup to run?
http://support.veritas.com/docs/249090
Please also ensure that you are not experiencing hardware related issues and that you have installed the latest device drivers, the SCSI card firmware is uptodate.
Please disable Removable Storage Service even if its Startup Type is MANUAL.
Hope this helps you further.
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