i recently used left 4 dead with vd and vorpx.
what i have to do is connect to virtual desktop, start vorpx, load profile to the game and click apply, then open steamvr alone i enter in the home, then i run left 4 dead 2, press ok when says its not a vr game, and works.
after the first time, you can launch directly l4d2 and vorpx gonna catch it.