If the tip of his arrow shimmers, he is preparing an Impaler Arrow. Avoid being pinned to the wall at all costs; his Planted will do 2400 damage before you can even move again, and likely another 2400 to follow, killing anyone.
If enemy team has a Tyra, you are most likely better off using "Crackshot" legendary since Tyra can counter your stealth and mitigate the effectiveness of your other legendaries
Use Pursuit only when the enemy is low on health since it doesn't do as much damage and if you don't kill them with it you could possibly die,since you are vulnerable and aren't doing as much damage to kill them.