The mic issue is a hardware fault. You should totally test all of them before buying, or maybe buying it with a warranty and send it to MS to repair. Software updates or resets won't fix it, and unfortunately it's common among 930s. There are some apps and softwares you can use to test them.
About the battery, I don't know about the 650, but the 930 running W10M doesn't last so long for me, at least not in its current version. Light use last me through the day, but if I push it a little harder it'll run out of juice before the day is over. If you're into gaming, lots of browsing or use 3G/4G a lot, be ready to charge your phone twice a day... Edge is very power hungry for me.
The rest, it's a very solid phone, superb camera, fantastic screen, great performance, etc. I just hope they get the battery use right.