If you do
/usr/sbin/vserver server exec command \*
You end up with \* passed to the command directly, without shell expansion. The /usr/sbin/vserver front-end is preserving the arguments as much as possible. So if you escaped something to prevent shell expansion, it will remain that way.
The trick is to use a shell on the other side (in the vserver). The command is simply rewritten like this:
/usr/sbin/vserver server exec /bin/sh -c "command *"