The best thing would be to have the possibility to chose wich decks should belong to the "random list". maybe with a checkbox near the name of the deck in the decks section (checked by defalult)
I like this idea. Perhaps they are included by default, but you can checkmark something to exclude it from being chosen at random. (Decks created for particular AI challenges come to mind.)
I never let it select a random deck because I have too many that I created for a specific purpose and not for match play. Also a few that I haven't touched in several updates and are probably terribly broken.