I'm pretty sure RBA or Goffin don't need to play the match of their life to beat a decent Dimitrov.
RBA playing the match of his life can beat Djokovic, so you're absolutely right about him. The same if true for Dimitrov of course. From what I've seen of Goffin lately, he would have to be playing significantly better than Dimitrov to win. I'm hoping for an RBA v Dimitrov final, since their matchup is far more entertaining.