Voids do not work in melee - this might be expected.
Actually, if you are within 2" your attack is within the void shield (which will always be the case in melee) so you can run up to a titan, get within 2" and unload on them directly. I tried this with my warhound but the Reaver went 1st and blew me to kingdom come.
I got a wildfire death result which meant I shot all my guns as I died, alas this is in a random direction and I hit nothing.