Black cleaver is mainly picked up by assassins, turning them into one-shotting bruisers

While the item is definitely good on bruisers and juggernauts, once again marksmen and assassins are perverting its intended use - by simply being much more effective with it than anybody else. Now cleaver makes assassins require ganging up on akin to a juggernaut to bring down, simply because they build full damage, then build cleaver, and cleaver being such a powerhouse it turns them from glass cannons into front line bruisers.