I really don't understand the idea that Bass is a proven defender against Lebron and Melo. When he guarded Lebron in game 6 in 2012 after Pierce got into foul trouble, he looked okay, meaning, he wasn't as awful as expected. When Doc went back to Bass in game 7 against Lebron, he got roasted like expected. There is no way Bass is a competent defender against Lebron. He's spent about 15 minutes of game time at most defending Lebron the past two seasons. Lebron is the most unguardable player in the game and somehow Bass is an effective defender against him? Yes, that's as absurd as it sounds.
Regarding Melo, the only success Bass had defending Melo was I think in game 6. All the games before then, he had had little sucess. But about that "success" in game 6. It wasn't anything Bass did. Melo sabotaged himself by pulling up for long jumpers even after he had beaten Bass off the dribble. This is sometimes the conundrum of Melo and his bad shot selection. After a few clanks and I suppose some talking to by coaches, he stopped pulling up for jumpers and repeatedly drove past Bass. So no, Bass cannot defend Melo. Again it's absurd.
Even if Bass had been outstanding in the 40 total minutes he spent defending Melo and Lebron the past two seasons, I think the terrible rebounding, poor awareness on team defense and the near total reluctance to take a charge outweighs whatever he accomplished in 40 minutes.