'Mental Divergence' reads "Power: Destroy 1 Ongoing card or ... " 'Weak heart' is an Ongoing, Jinx card that is played in front of a hero and reads "Whenever that hero uses a Power, Kismet deals that hero 1 psychic damage".
If 'Weak heart' has been played in front of Visionary and she uses the power of 'Mental Divergence' to destroy 'Weak heart', is she still dealt the 1 psychic damage from Kismet? We have played it as she does take the damage.
Unless I'm mistaken, the reaction damage goes off after the power has completed its effect. Nothing is truly simultaneous, remember. By the time Weak Heart can go off, it's already been sent to the trash.