They design the game and rewards, they know how to do this properly but they keep pushing massive RNG that leads to this kind of behaviour, they could fix it by implementing good BLP, a 1 attempt per account with good drop %, so players will do only their main.
Remember even reward dev mentioned that the best approach “it’s in your best interest to repeat this event every day on as many characters as possible. That’s… mathematically correct, but not a great experience.”
A lot of players are doing that and they don’t manage all classes, the boss got buffed and other players don’t wait for a spec change.