Some thoughts on supports.
Preface: I haven't read every forum post and I'm sure I will mention things other people said.
Some champions gravitate toward the support role because they have more utility than straight damage soak or kill potential. Riven has an obnoxious amount of cc, but unlike Leona whose kit is geared toward locking people down over and over while not dying, Riven's kit is geared toward locking people down and killing them as quickly as possible, cause she is squishy. So Leona is a support and Riven generally isn't. Healers, ally buffers and disruption slingers, and even high impact harassers like Cassiopeia all make appearances as supports. But balancing them is a pain, mostly because of the way they are built.
Damage dealing champs scale off of ad and ap, and that's fine. Some champs have hp or mana scaling, and they are rare enough that Riot can handle them on a case by case basis to keep them in line, even though Ryze has gone through more reworks than a celebrity in drug rehab. The problem is that supports scale the same way and most utility doesn't scale at all. This means that stuns, slows, buffs, etc all lost as long as they last, slow as much as they slow, whether you have no items or full build. Buying ap on Sona makes my heals more effective, but that's about it from a utility standpoint, my slow doesn't slow more, my ult doesn't stun a bigger area or last longer. Leona's great lockdown is exactly the same no matter what she builds. Braum's item choices are all going to focus around what makes him hardest to kill, since his utility is all about staying alive long enough to keep using his consistently effective disruption skills. Buying ap items make Soraka or Nami better healers, but all the ap in the game wont make their cc more effective, won't change anything about their slows or silences or lockdowns.
This is a major factor in deciding which champs to take as support in a gold starved support world. There was an attempt to address this issue with gold generating support items, which helped supports fill item slots but didn't really change the way they shopped or played. Because for a support, you want someone that doesn't need to get fed to be useful: you will never get fed. This makes consistently powerful cc and buffs very attractive, and items are for staying alive (and warding, nobody else will anyway, right?) such as tanky or sustain items, or maybe ap for heals and shields.
But this whole thing is unhealthy. First, there isn't much choice in what to build for supports. Sure you have to pay attention to mr vs armor, and how much cdr can I afford right now, but when did a Taric support ever consider building anything not from a list of the same 6 or 8 items each game, regardless of who the enemy takes? It feels like supports are even more gated in item choices than adc's are. Damage and healing/shielding scale, nothing else does, so unless you have heals or shields on your support, its time for a Deadman's Plate and a Spirit Visage, or one of the other interchangeable situational support items. At best, its boring.
Second, it makes balancing a nightmare. Unless Riot permanently locks certain champs in to a support role, thereby cementing a meta, something they have repeatedly claimed to not want to do, each champ needs to have the ability to do damage or they would never be playable in a solo lane. But at times when Lulu or Soraka have been scaling well enough off ap to be practical in a solo lane, they have just been a complete nightmare to play against. They still had all that innate utility that made them worth playing as a support, but now with enough damage output on top of that to dominate a lane. But there is no way to balance a champion by nerfing some of their utility to preserve their solo lane potential and still expect people to play them as a support; to make them viable in a solo lane you would have to remove too much of the utility they need to support in a duo lane or teamfight.
Third, if Riot boosts the gold for supports again like they say they want to, it makes the supports who are kind of balanced around being a little gold starved, like Leona who has all the utility built in to her kit and just needs to build items for durability to keep spamming cc, a little broken. Suddenly, these champs would have access to more stats and activate-able items earlier, skewing the balance of power curves for various champions out of alignment.
Fourth, many find the gameplay to be unrewarding. Sitting in lane on high alert for ganks or enemy initiations while most of the time doing little to nothing, being in charge of warding because you are just the support, you don't need damage anyway, you will just take my kills (please note the sarcasm), etc...
I'm sure I missed some things.
I would like to propose that to fix this, cc and utility gains scaling.
This can be done one of 2 ways. The easier way is to make cc scale the same way healing and damage does, for all champions not just supports. This would give Riot more flexibility in balancing individual champions, as well as balancing cc as a whole and giving players more options in how to play each champion. On an individual level, utility could scale off ap, ad, hp, mana, move speed, whatever Riot decides is appropriate for each champion. Items could be introduced or changed that deal with cc and buffs on a more interactive level beyond just Boots of Swiftness or Merc Treads. This would also give players another playstyle option, letting them choose to take the base stats on their abilities and build up other areas or to focus on maximizing the direct impact of their durability. If Leona's base cc on her skills was shorter and her shield less powerful but her skills' utility also scaled off ap, it would open up build paths that give her the choice of building ap items that enhance her utility or focusing on being unkillable and leaving her cc at its base levels. Or Cho'Gath could have the damage on his silence and knockup scale off ap, but have the duration scale off hp or ad. There are lots of options.
The second way this scaling could be realized would be a little harder, I think, but would offer more possibilities. Replace Ability Power with Magic Power or something more equivalent to Attack Damage, and shift Ability Power to what I think it should have been all along, which is a measure of the power of abilities, or utility. This would be a new, separate stat that would affect things like shields, heals, stuns, basically everything that's not damage. This new ap stat could have its own itemization for players who want to focus on longer stuns, better speed buffs, etc. Or shields could scale with damage, and healing with utility, there are plenty of options. Sona could choose between focusing damage for her Q or ability for her shield, heal, slow, etc. Mages like Veigar or Ahri could choose between the straight damage on Rabadon's Deathcap, the damage and sustain from a Rod of Ages, or a new item that gives damage and the new utility stat that enhances their respective cc in some way. Veigar's net could stun people longer, or the net itself could last longer. And tenacity could become a defensive stat like armor and mr. There could be utility focused items, hybrid items...
I think the second option provides more flexibility and options for new mechanics and balancing, but I recognize that 6 item slots can get crowded when you add even more stats that people want. But it would allow for balancing a champion with high utility for separate build paths if they want to maximize utility for support, or maximize damage or tankiness for a solo lane.
Thanks for reading, I know it was a bit long. Thoughts?