Get a mic pre amp between the mic and the mixer. I use the TC Helicon Voice Tone. I picked up a used one on ebay for about $100. Better yet record your audio separately with a recorder and sync the camera audio to the recorded audio then mute the camera audio in the editor. Camera audio cannot compete with a separate recorder. I use the Zoom R16 which has 8 inputs.
For video editors, finding the perfect portable workstation is like catching a unicorn. It is no easy task to find the perfect balance of performance vs price point.
