Patch 7.11 was the patch of Doran's Shield. The changes to the Shield that shipped in 7.11 changed an item that was previously situational at best into one of the most versatile starting items that the game has ever seen. The existence of Doran's Shield fundamentally changed the dynamic in all three lanes, as there was no level of harass that was too great to be absorbed. Everyone from Shen to Lucian was buying Doran's Shield at the start of the game, and it wasn't unusual to see five Doran's Shields in any given professional game. There are no two ways about it, the item was broken.
Enter Patch 7.12, or the patch that was supposed to save us from the Doran's scourge that had overtaken the Rift. Doran's Shield and Ring both ate nerfs that targeted their abuse cases. Top lane Gragas could no longer stack Doran's Rings and get all the effects of a Rod of Ages at a fraction of the price, as the mana restore passive on the Ring was made unique. Doran's Shield was dealt no such heavy blow, however, as the items price was just increased by 50 so as to make it impossible to start the game with both a Doran's Shield and two health potions.
The reaction from the player base has been extreme, to say the least. Doran's Shield fell off the map as a starting item nearly overnight, even amongst the champions who most appreciated its sustain. The effect was most pronounced in the ADC role, where the item has all but disappeared despite its ubiquity just a single patch ago.
That shouldn't have been the case, though. The reality is Doran's Shield didn't take over the bottom lane solely because it was overpowered, it took over because the other starting items it was competing with weren't all that enticing themselves. Players have been looking for alternatives to Doran's Blade as a starting item for the entirety of Season 7. Was Doran's Shield really all that improbable of a starting item on a role that was already starting the game with boots and potions on occasion?
The reality is that Doran's Shield offers far more desirable stats than it offensive counterpart for the majority of ADCs. Lifesteal is nice and all, but it's also difficult to use when there's a Caitlyn and a Karma/Lulu/Zyra on the other side of the lane. Doran's Blade asks it's wielder to auto attack enemies in order to access its sustain. Doran's Shield simply asks you to stay alive. It doesn't take a genius to figure out which condition is easier.
The TL;DR is this: for most ADCs there's nothing more valuable during the early game than sustain. Sustain helps you stay in lane to farm your B.F. Sword, Cutlass, or Zeal. Doran's Shield is still a better sustain option that Doran's Blade for all safe Caitlyn, and making it cost a potion's worth of gold more isn't going to change that. The change in 7.12 certainly helped bring Doran's Shield in line, but it didn't make it underpowered, merely fair. If you're planning on taking a Kog'Maw, Tristana, or Twitch onto the rift, then Doran's Shield is still your best friend, even after the nerfs.