Hey guys, I've actually been a warlock since 2004, so I will answer you questions regarding why he didn't curse his opponents before the fights:
In black magic, when placing hexes we generally need to have some sort of piece of the person - a hair, some blood, an arm, etc.
Mir must have gotten some part of a fighter before some of his fights he had won, but been unable to get a piece in the fights he lost.
This is apparent in the weigh in at Cheick Kongo. He must have gotten something from Cheick Kongo and wasted no time in placing the hex, right there at the weigh in!
Hope this clears some stuff up.