/removeav is the right option, at least for Landesk8.8 - I used it myself last week.
"C:\Program Files\LANDesk\LDClient\vulscan.exe" /removeav /showui /RebootAction=never
I don't think it keeps a logfile though, but with the /showui you can at least get some feedback on-screen. Note that the uninstall will be delayed if there are other installations or vulscans in progress.
The uninstallation should be logged in the Vulscan.log (or vulscan.#.log) in the C:\Documents and Settings\All Users\Application Data\Vulscan directory (or ProgramData\Vulscan on Vista and newer)