Willo's hitbox is very large and she's slow so you have the advantage if you're able to aim for her wings. If she decides to fly away from her original location, don't track her, predict where the arch will slow down at its peak and shoot there.
Can Take her out fast with a quick left click followed by a pounce... Very satisfying... Code name 1-2 combo, Follow up with a question of "do you want fries with that".
Grover can do a lot of damage to your teammates trying to get on point. Consider flanking to Grover's Spawn's side and shooting him. This will make him have to focus on you and not killing your team. May throw off flankers for a bit. STILL DANGEROUS!
Something you should always do is focus fire. If Ying has the Life Like Legendary Card, this is even more effective as the heal beam loses 30% of its healing ability, but if you spread out the damage, she will have 40% extra overall due to 2 beams.
Assuming Buck hits you at point blank with all his pellets in the head, he will need 3 shots to kill you.(2.8s) This will never happen. You can knock buck down to 500 HP with the Daggers+Pounce+Daggers combo (about 2s). Easy kill from there.