Singed rework and balance issues
I often criticise Riot for the way they are balancing the game and Singed in particular, but I haven't added a lot constructive myself. Maybe if we are lucky, Riot will see this thread and take this feedback and constructive criticism. And to make it even more comfortable, I will make a couple of own suggestions for a future rework/change.
For background, I'm Ankan on EUW and I have been a high elo Singed main for 3, almost 4 years now. Since Season 3, I have been Diamond 1 or higher, often poking into low/mid-Master (50-200 LP). Season 4, I was the best Singed in Europe, arguably the World. I have played Singed from his insane Season 2 day to his weakest time, which is now. I have probably in total over 2700 Singed games if you combine the games from all seasons on my three active accounts.
Singed's main problem
One of the biggest problems I have with Riot's balancing team is that they make changes which aren't influencing the issue that the champion is having. A good example of this is Riot's buff to Singed's ulti stats (60 ⇒ 80 Level 3) or the buff to Olaf's W (9/12/15/18/21% ⇒ 14/16/18/20/22%). Olaf doesn't need more lifesteal to become viable. It doesn't help his core issue. It's like giving a starving family new shoes. It doesn't make them less hungry.
Singed doesn't have poor base stats or poorly tuned spells. He has okay scalings and a strong steroid. The last couple of years, Riot has even made them better, for example giving him back his scaling MR. So what is Singed's problem really? He should by all means be a strong meta pick, just looking at his stats in comparison to other toplaners.
Singed's problem lies in his lack of tools to deal with the strong allround champions released the last couple of years. Every newly released marksman or AP caster has tons of tool to deal with a champion like Singed. A champion like Kalista has a tiny escape twice per second (midgame/lategame), a slow and a reliable knockup. There a couple of exceptions to this rule, but the amount of escapes and CC in the game is incredibly high, making it extremely hard for champions without gapclosers or longer range to get a grip in the meta.
Singed doesn't need more damage, armor or magic resist. Singed needs a new tool to deal with kiting. The only way to deal with a good kiting ADC (every ADC in higher elo) is to build full tank and just play try and get a lucky flank in. Building any larger amount of AP (which I'll touch on later) is not viable anymore, because you get blown up while CCed in these kite-situations.
I can imagine it being really hard to balance now, especially since Riot has upped Singed's other stats and spells, but it certainly has to be tested. I understand that it is impossible for a team like the balancing team to know every champion in the way like a high elo OTP does, considering there are so many champions right now, therefore I'm not even upset. What I'm upset about, is that Riot doesn't reach out to the best players in the world and ask them what the problem with their champion is. There are so many genuinly passionate players out there and I think it's a big shame that they aren't approached. Instead the General Board is asked about suggestions for a new Singed passive (which really is the worst place you can ask for balancing tips).
Riot Pls Singed
So now we know the problem with Singed. What do we with him then? I have talked a lot with the best Singed OTPs in the World for years and I think most of them agrees that Singed needs a passive. The tiny HP boost is nothing against what a lot of other champions becomes. The only thing the passive does is baiting newer Singed players into buying Mana items. Forcing us to buy non-combat stats on a champion that really needs combat stats to survive Season 6 marksmen/AP-casters/supports to get something out of the passive is not very good. Riot has come up with so amazingly innovative and interesting game mechanics for passives and spells the last couple of years, but Singed still has HP for Mana. Giving Singed a passive that actually deals with Singed's problem is probably the only thing needed for him to become an okay pick again.
I have seen simple suggestions like giving Singed Vayne's passive, giving him more movement speed running towards champions, but in reality, this won't deal with the problem of Singed getting CCed and kited to infinity. Singed needs either a reliable range CC to pin players down or a way of becoming unstoppable (a lá Sion or Udyr).
I like using the theme of bottles. I love the new set of 'toxins' in the upcoming Hearthstone expansion and would love to see Singed getting something like that as well. A rotating set of potions or toxins that he can drink/throw at his enemy with different boosts/stats? Perhaps even giving him the option of buying them in the store instead of normal potions.