An entire class of Support champions is not viable.

I have been a Support main since Season 1. And while I love the changes that they made to the role a few years ago, it's no secret that Support champions like Lulu, Nami, Sona, etc have fallen out of the meta. Even champions like Janna, and Annie don't build Spellthief's anymore. The similarity that all of these champions have is that all of them scale with AP harder than other supports, and benefit from builds with AP. Janna and Annie found salvation by being able to survive with less AP in their builds, instead choosing to build other Support items. But the rest need AP in order to scale. They cannot scale as hard into the late game with Ancient Coin because their supporting abilities need AP to have any impact. Many Support players understandably have ditched Spellthief on these champions in favor of Coin. Right now, these Supports still buy Spellthief's because they have to, but they suffer with it, and clearly aren't viable competitively.

         The main problem with Spellthief Supports is that there are very few good Support items that give AP. Spellthief's Edge, Zeke's Harbinger, and Banner of Command. Banner of Command is not an item that a Support should build every game, because it isn't always a good item (For example if the enemy team has a lot of AD). The active on Twin Shadows is terrible, and while you sometimes see these Supports build that item, it shows how these Supports need and want the stats, but can't afford the more expensive AP items. And while these Supports can use bigger AP items like Morello's, Deathcap, and Rylai's well, they rarely have the gold income to afford them as part of their standard build.

         My solution is that we increase the on-damage gold generation on Spellthief's Edge. What this will do is allow AP Supports to better afford bigger AP items, and scale into the late game harder. It will also make them have more of an impact in the laning phase, because they will have more of an incentive to poke and harass in lane. The upsides to this are that Annie, Janna, Nami, Sona, Lulu, Zilean, Soraka, and possibly even Bard get more room to breathe with their builds. They will be able to afford the AP that they so desperately need. The downside is that Annie might possibly stop building Ancient Coin in favor of Spellthief's and become too strong. However, it shouldn't be a problem if we coupled it with some well deserved Annie nerfs to make her less oppressive with high amounts of AP.

TL;DR: Supports like Nami, Sona, Lulu, etc, need AP in order to scale, but can't afford it. Proposed solution: Give Spellthief's more gold in order to let them better afford big AP items.