Lucian's Culling

When ulting a wave of minions with close to 300 AD, I kill 2.5-3 melee minons when I used to be able to kill a wave. This has already lost me some kills as the enemy just walks behind a melee minion and half of the culling damage is negated. Did the 400% increase in damage to minions change to a 400% increase in resistances?