Nasus ain't even op though. If he picks it, pick jax or trundle and you win the lane and the teamfight. Jax just gives no fucks about nasus early game and scales hard enough to deal with him late game, while trundle gets to make nasus his bitch pre and post 6 because of his q and r.
And braum is op only because he has enough offensive tools that he really can just dive in and force engagements, but so much defensive mobility that he might as well initiate, take the brunt of the damage deliberately becuase of his 4 seconds of 40% damage reduction, which can have a 6 second cd, ignoring the fact that he also gets 20% of his armor and mr buff for 3 seconds, on another possible 6 second cd, because he can just use that to waltz right on out because 40% extra damage reduction puts him easily at 64% damage reduction with no pen against his stats. It's basically a permanent alistar ult. And like alistars ult, pen items only go through his stats, not the auto reduction, so there's no itemization against it. He will no matter what, even with the highest pen possible and considering likely build paths, have at least 46% reduction in total. And he often hits 3k to 4k health, so you can't afford to focus him, and pray to god that you have a source of persistent damage to whittle the fucker down after the fight.