well, to put it simply, 4 AD only interrupts how the champion feels to play and barely makes an impact on their actual damage
basically, what I meant is that you have to change your farm pattern to be more in line with the minions
let's take aatrox for example. If you lose that 4 AD, overall, he would only lose 14 damage from his kit and his farm would be more annoying but this would only slightly influence his gameplay pattern by cutting down some of his gold income
in the grand scheme of things, Aatrox for instance starts with 510 hp
14 damage out of 510 not counting armor is about a 3% increase in what he needs to kill a target and fairly negligible
if you throw auto attacks into it, if you somehow engaged in an encounter long enough for 10 strikes, it would reduce his damage count by one BF sword while still doing 560 to 1410 (assuming they took it from total as well) damage before armor in those attacks
if we take the base armor for him at 33, it's roughly 75% damage taken, or 421 damage from autos compared to 451
this is an extremely long extended trade and makes a negligible impact at the weakest point in the game
if you somehow got into this skirmish at level 1 and managed to hit all of your Q in sweet spots, the damage comes to about 578 or so or enough to "kill" the target, and that's not counting his passive damage or the runes
it's a difference, but a small one that ultimately does not change the result
changes to base AD only affect the champion's farming phase, which can be good if you know where to interrupt it, but otherwise, not much changes