If we have the Kayle Curse, what about the Braum Effect

Your lucian will always dash into cho's rupture, ani/leona/sej stun, mf ult.. Attack the full health enemy champ instead of the one that is doing the dmg and has 10 hp left.. RNG RNG RNG

This is simply a case of the AI choosing to attack the closest champion. It's actually a critical component of being able to structure a backline and frontline, and a healthy part of the game. If everyone avoided Braum until the end of the battle, he would be worthless. We've got to let the tanks tank without complaining that they're distracting from the squishy carries; that's literally the whole point of their existence.