Mirage Deadeye Just Plain Bad

Is Mirage deadeye ascendancy as bad as I think? I thought I would automatically get a cool DPS producing Mirage. Then I searched for hours because it wasnt working at all to find out I had to drag another already equipped skill gem into the slot, thereby LOSING the ability to use that skill. I found a couple of other guys trying it that had the same issue so I think we are doing it right, but why do we lose one of the good skills we are using? Shouldn't the mirage mimic what we are doing, and using for skills? This seems like a huge waste of ascension points unless we are all doing it wrong.