Is there some way we can view all mixes or sort them or search for them? Just hitting refresh over and over and hoping to get lucky sucks. What am I missing?

There isn't a way to do this yet, unfortunately.

You can sort them by date or by votes only. There is no search mode.

The best way to browse the GOGmixes is probably to visit the game pages of games that you like. GOGmixes that include that game will be displayed there, sorted by number of votes.