Grover's axes do so much damage at long range, that Grover can potentially have more damage-per-second than Kinessa at a certain point, making him a strong option for dealing with her at a distance.
Encountering Grover in long range open spaces - don't PEEK around the corner.
Good Grover players throw axes preemptively and you can take a lot of damage. Use short sprints between cover. This way it's harder to predict where to aim.