Patch 7.9 might have been a patch directed at the League's tanks, but that doesn't mean that tanks got all the goodies. In fact, the mortal enemy of tanks everywhere, ADCs, also got some new tools to play with. The most obvious of these is the new Guardian Angel, which features Attack Damage now instead of it's previous mitigation stats, but it's far from the only one. In fact, hidden in the patch notes was a change that, at first, seemed more a nerf than a buff, but it may instead prove to be the key to some new forms of ADC itemization.
The change I'm referring to was the rebalancing of the Zeal items. While Runaan's Hurricane, the most heavily used of the three, was simply nerfed, both Static Shiv and Rapid Fire Cannon got a few touches that put them back near the state that they were released in. For Rapid Fire Cannon that more ranged on the empowered auto attacks at the cost of damage. That damage was transferred over the Static Shiv, which was almost never purchased prior to 7.9. Basically, Riot wanted to make Rapid Fire Cannon more about the range, while Static Shiv would be the go-to purchase for sheer damage. These were not the only changes that were made, however.
When Rapid Fire Cannon was first released, it's ability stacked with Static Shiv. Purchasing both of the items would not only allow you to benefit from Rapid Fire Cannon's extra range, but the outstanding waveclear and burst damage that Static Shin offered as well. Purchasing both of them became the norm for auto-attack heavy champions such as Caitlyn or Tristana, both of whom bypassed their traditional mid-game power trough thanks to the incredible burst damage the two items offered. Anything short of tank couldn't hope to take a hit from an ADC with both of the two items without losing half of their HP, a fact that eventually resulted in a change that made the two items mutually exclusive.
It seems Riot believes that critical-based ADCs have been sitting in the doghouse long enough, however, as Patch 7.9 included the biggest buff that they've seen in some time. Static Shiv and Rapid Fire Cannon now once again can activate together, and Riot even outright incentivized players to purchase both of the two items together by changing their damage values. What does that mean for all of you ADCs out there? It means that the times may quickly be changing, and the rise of Caitlyn, Tristana, and even Vayne may not be far away. For the moment they are being kept in check by the powerful lane-dominant picks like Draven and Miss Fortune, but if either of those two see nerfs in the future, then expect the Infinity Edge carries to come back with a vengeance. Above all, be aware of the interaction, and don't look to trade with an enemy ADC that is stacking the two items. Blade of the Ruined King might offer excellent sustain, but it doesn't come close to rivaling the damage that a Shiv/Cannon combo offers. Be careful before you mess with that Caitlyn, and good luck to all of you as you hit the Rift in the coming days.