Here was me grappling with checking my audio sync between two cameras and 4 channels from my Edirol R-4. Mute this, solo that, oops I just soloed a video track. What an unpleasant experience. Then the lightbulb went on. Route every source / group to a buss. Problem solved. One mute/solo button for R-4, one for camera A, one for camera B.
Don't have to follow my scheme, make up whatever suits you. Some of mine now get a bit more complex as I like to put compression on a buss so I then route that to another buss which handles the mix from all the R-4 channels.
One tip you should follow, label everything.
One area where Vegas still beats the pants off every other NLE is audio.
Bob.