From the below links i believe your PCIE raid controller and the pass through device sharing the same PCIE bus...I am not sure 100%,
I have previously configured the passthough in the DELL server, but at that time it was on board RAID controller,
Note: The configuration changes are saved in the /etc/vmware/esx.conf file. The parent PCI bridge, and if two devices are under the same PCI bridge, only one entry is recorded.
The PCI slot number where the device was connected is 00:0b:0. It is recorded as:
/device/000:11.0/owner = "passthru"
Note: 11 is the decimal equivalent of the hexadecimal 0b.
And also from the Symantec http://www.symantec.com/business/support/index?page=content&id=TECH70246
"Tape devices should not share a BUS with any other non-tape device, and should be given their own dedicated SCSI controller."