How did I get it last night when I was popping assassin droids standing in the opposite corner away from the droid?
Dumb luck unless the game glitched.
We have people who don't have the minesweeper title takes turns standing underneath the boss. This way we know ahead of time who will defuse, and we can hope to spread out the titles. Never fails for us, the person underneath always gets it.
(If you watch methodicals 16 man HM video, they use the same tactic.)