Verify does a CRC i.e Cyclic Redundancy Check and that is a Best Practice that Symantec Recommends.
It checks the data arrived to server and data written to Tape and if it finds any discrepency or the value does not match then it reports an error about unable to verify
I am sure the other vendors would also suggest the same.
If its too much of an overhead then you can just untick it and I am sure not many times you have to get in the policy to make changes.
The question of disabling the verify option permanently can definately be posted as an enhancement request.
Just in case you are not using verify since its taking almost the same time as backup then make sure you report this situation to the Device Manufacturer. Verify should take much lesser time than Backup.
Also the only reason why support would have said not supported if verify was unticked is because it does not want the customer to get accustomed to this habit of disabling the verify since any errors due to tape drive or network or other factors which might cause a verify failure or CRC errors would not be brought to the administrators notice and hence this could land him in a disaster if he finds out that the tapes are not restorable since the Tape Controller or Tape unit was not writing correctly or maybe an Issue with read head wherin its not able to read the tape properly and during restore you might find out that the library read head it bad and then attend to 2 problem rather then resolving one.
