To be honest, I don't quite understand the importance of a backup QB unless you have an elite team all-around. If your starter goes down for any length of time, the season is done, no matter how decent the backup is. If Tannehill goes down, I'd rather just tank the season and get a high draft pick, rather than do what we did in 2011 and string together a few meaningless wins with the mediocre backup to get out of position for a can't miss QB prospect like Luck. In that regard, I'd rather have a high draft pick than Moore as backup. That being said I wouldn't give him up for a late-round pick.
I suppose the true value of a solid backup QB is win the starter gets knicked up for a game or two and the backup can come in and keep things afloat, but eh... I'd roll the dice that another backup could still pull off a game or two with the right surrounding cast around them.