You have to memorize over 150+ of his moves, knowing the opponent and their character pick, and the approach Brad Wong does knowing the consequences and the risk you have to take. I'd definitely would like to give him along with Raidou and Pai top 3 regarding skill cap to win games.
I don't know about that, Ayane is pretty damn difficult to play. More than most realize. I would say the 3 Force listed and add Honoka and Raidou to that list as well.
4 stances, with different variations, over 150 moves and mandatory fundamentals? Yeah, as with all Zui Quan practicioners in fighting games, Brad is THE hardest character to play in DOA, there's even meta that applies only to him.