Garcia is the obvious one. Battle, Hawkins, Odukale, Patterson, Willis, Cooper, M. Mitchell, Fox. The last two for sure would probably be better served as bench options on good teams but Johnson has brought in a number of good solid players.
All of his rosters have had clear flaws and the results haven't been good enough but that doesn't change the fact that he has brought in some good transfers. Just not enough of them to get the team to the point where it was competitive with the top of the conference.
It's the main reason I would make the change after this year knowing that the roster is going to need to be rebuilt again and to this point Johnson has not shown an ability to get the players he needs to take the team to the next level.