This question isn't in regards to AV for e-mail traffic, SPAM software, etc. as we already have that deployed both on the Exchange server (SPAM/AV software with GFI) and in our ASA router (SPAM software, network AV, etc.).
This is more the file system AV (Symantec) that we have already installed on the Exchange server - is it necessary? The Exchange server is only operating as an Exchange server.