Joon - If the only desire is pure attack, he still needs a support hero if you are going for the kill. He is pretty weak on overall survivability but the best s1 snipper.
But I love Bai. In the current meta there are way too many heros that are AOE damage dealers.
Bai makes sure that he blinds such heros. I still use him at 3 70 waiting on darts. He makes the enemy heros miss all the hits, I have never had a hero successfully hit me once Bai hits them. It depends on ur game play. Malosi though neutralizes the Enemys spl, but he still allows them do direct damage. Eg, Alfrike will not cast the mindless attack but she will still deal enough damage with her cubes, but Bai makes sure Alf doesnt land 4 outta 5 cubes on you. Joon rarely kills Alf without a def down and his miss is just meh most times.
If you lack finishers Joon it is, but Bai is a spl panda.