The sixt helix that let you fire 2 rockets at once dont work . On incursion i had used it once but on echelon it did not work
It worked fine for me, just gotta hold down the mouse and make sure you got 2+ rockets ready to fire.
When I first unlocked and used it in story mode it was not working. It fired rockets normally. However when I did get it working (in a versus mode) I found out how useless it is. For me at least