When, how, and why did Lucian suddenly become a problem?

The following are the last 5 patches that Lucian got changed in. I want someone to explain to me when he became a problem, because unless it was just in high elos, it wasn't right after the Marksman update. The most recent changes to Black cleaver were also nerfs in damage and health, but the combine cost got lower and the cdr went up to 20%. Is that when something happened? I want to understand if this is actually something worth my attention or just another case of "We didn't notice Brand for 3 years, but now he's suddenly op wow Riot how"

V6.7:

The Culling BUG FIX: Fixed a bug where The Culling would sometimes be interrupted even if he had a spell shield.

V6.4:

The Culling Range reduced to 1200 from 1400.

V5.23:

Stats Base attack damage reduced to 57.46 from 59.46.

The Culling Base damage per shot changed to 20 / 35 / 50 from 40 / 50 / 60. AD ratio per shot changed to 20% Total AD from 25% Bonus AD.

V5.22:

Stats Base attack damage increased to 59.46 from 52.04. Attack damage growth reduced to 2.41 from 3. Base mana increased to 348.88 from 298.88. Mana growth reduced to 38 from 41.

The Culling REMOVED: Attack Speed scaling. NEW EFFECT: Now fires 20 / 25 / 30 bullets.

V5.16:

Lightslinger Second shot damage increased to 30 / 40 / 50 / 60% AD from 30 / 40 / 50% AD. Damage against minion increase to 100% AD from 60 / 80 / 100% AD

Ardent Blaze NEW EFFECT: Allies can trigger the bonus movement speed for Lucian. Movement speed increased to 60 / 65 / 70 / 75 / 80 from 40 / 45 / 50 / 55 / 60. Movement speed duration reduced to 1 second from 2. Mana cost reduced to 50 from 60.