"Breakout" is obviously a non-quantitative term. You have your definition (which is fine) but mine is more along the lines of a name that goes from a role player (or unknown) to national recognition. Sure, Hand, Foster, Evans, and Harrison were great role players for the 2015 team and they certainty played a valuable role in the NC Game.
Think about last year, going into the '15 season. All of us on this board knew who Tim Williams was and knew what he was capable of doing. But he went from an Alabama known, to a national known during the season, thereby "breaking out" so to speak. I doubt anyone on here would have said TW's breakout season was 2014 when he played a role and flashed his potential. This is where I see the players you list right now, they are Tim Williams between the '14 and '15 season.
But like I said, opinions vary and that's what makes discussion interesting and fun. Cheers!