He loses to mind. The next month he loses to Stork 0-3 , the player whom he beat 3-2 in the previous MSL finals and barely beats Upmagic! (horrible tvp) 3-2 in the qualifers. How does that not constitute as a mental wreck? Yes he may have lost to Jaedong in Gom MSL 4 in that classic game, but he also lost to YELLOW ARNC, whose career 47% ZvP makes even his also horrible brother Luxury seem like a strong ZvPer.
Then loses to an off form Iris 0-2 in GSI. His play in Bacchus wasn't *bad* per say (game vs Flash on Katrina was pretty nice) but it was hardly great either.
I think his performance in this period is underrated, but there is absolutely no question that Bonjwa Bisu died the moment he lost to Mind. You don't just get raped 0-3 to a player whom you beat six months earlier. Bisu in his prime would never be eliminated by Yellow[arnc]; that evidence along is enough to discount any rubbish of Jaedong beating him in his prime.