The HF8 is designed to work with the HFS program to provide feedback based on the telemetry data received from the games on the list of compatible games. The Virtual Sound Card mode is designed to allow for non-compatible games to provide feedback based on the audio signal whilst operating in the USB Mode. Adjustments will need to be made to the sound levels within each games' audio menus.
It sounds like your unit is operating as designed. In order to have more control over which motors are vibrating for which effect, you will need to play a title that is on the list of compatible games, along with activating the corresponding profile by clicking on the thumbnail in the HFS homescreen.