Don't get me wrong, I totally agree with what you're saying, Sona is definitely worse now than she ever was as far as I can remember. All I'm saying is Sona's already pretty decent poke is greatly augmented by Lich Bane and other items. I'm not saying it's particularly easy to do or anything, all I'm saying is the single target burst potential is there and that is definitely a factor in why she's in the state she's in right now.
As far as other supports go, you can definitely build AP on some of them and do pretty big damage. But none of them can utilize Lich Bane the same way Sona can to do 20-40% or more of the enemy midlaner or ADCs HP in a single spellcast+auto and even more if she gets her Staccato in there.
Here's what I think about Sona's situation, feel free to disagree with this section
Sona definitely needs work, I agree, but just straight up giving her better scaling without taking in all the factors would be reckless. And yes, items, any items no matter who can build them or who they're meant for, are a factor when it comes to champion balance. It clearly shows with how Riot is treating Sona. Lich Bane makes Sona stronger than she really is, that is true, but it's also why she's kept low to compensate. They could nerf Lich Bane, but that would hurt other champions that use it for damage. So, as much as you and I may dislike it, Sona takes the fall. If they were to buff Sona, it would have it be in one of a few ways:
- They could rework Lich Bane so that Sona doesn't synergize with it as well, but that would likely make it unviable on the other champs that use it too, so that's not an option
- They could rework Sona again, so that her Q or everything about her works differently
- They could lower her Q scaling so that she does little to no damage without Lich Bane to help, allowing her other skills to be buffed so that she doesn't feel overwhelming in bot lane
All of these options are pretty shit, right? So what is Riot supposed to do? Either every Lich Bane user suffers or just Sona suffers.
Despite all this mind you, Sona actually has a decent average winrate in plat+ ranked, almost 52%, according to champion.gg. Here we see her winrate fluctuates to even higher with a certain number of games and interestingly comes back down with even more experience for some reason. And, contrary to what Pika310 so angrily tried to shove down my throat, Sona does more damage than the majority of supports. She sits at 8th for damage, and neither the most frequent nor the highest winrate builds even look at Lich Bane until the last item.
Of course, when it comes to healing she's hilariously outclassed by Soraka and even Taric, but they rank among the lowest when it comes to damage. Even Nami, who is just above Sona for healing (about 800ish more), isn't even close to Sona's damage. There's a pretty noticable trend to be seen there.
Keep in mind this is all from a different source than the one Pika310 links in another post, which takes into account all ranked queues and not just plat+, where she's less popular than lower elo queues.
These are just the facts.