Slow vcenter backup speeds

We have Backup Exec 2012 (SP1) installed on a physical machine, backing up a VMware environment. (5.0) to tape library.

When backing up via vcenter we get around 450MB/Min

When backing up via remote agent we get about 1800MB/Min.

Backing up physical machines we get between 1500MB - 3000MB.

Any ideal why backing up via vcenter is so slow?

I have tried backing up via ESX host, however we get the same speeds.

We have Trend Deep Security installed, however even when it is turned off the backup speeds via vcenter stay at the same speeds.

Any assistance would be appreciated.