So alot of tanks r using black cleaver now for more dmg, is that why it was changed?

Not sure I understand what you're saying. Wouldn't improving on the current meta be a good thing?

Tanks deal more damage, but they also take more damage from AD sources. This is a huge buff to ADCs in the midgame (pre-LW) if they group with their cleaver teammates.

Tanks or just tanky champions? There's a reason there's the term bruiser.

You think BC helps the tank meta? Rofl...