Mist Stalker does not poison anyone

Mist Stalker’s power states:

Deal x damage to the weakest enemy. Poison them. Gain 3 magic if the enemy dies. I have been using the Mist Stalker in a team for the entire week and he has never poisoned anyone.

See example of an attack below:

Before attack

After Attack
I would show the result, but am only allowed one screenshot.