I can honestly say I've never won a lane against singed. I'm not going to sit here and rage "Oh my God Riot op nerf" shit. However I've researched his abilities a bit, "haven't used him yet, which I should for best results. He just doesn't seem like he can possibly be outplayed since skill isn't required for his insane hp and ap scaling. He has a slow, a knock up, and a speed boost that I'm pretty sure doubles his speed. Granted the speed boost is his ult, he still has his passive, and with boots of swiftness, no amount of cc can stop him unless it's a root. However all he has to do if rooted is pop his ult after 2 seconds, catch up to you and then his passive kicks off again. Mr doesn't matter since he can just get void staff, even without it he's so tanky and fast you can't stop him.
I know I've just sat here and talked about how he's almost invincible, but with the champs I use he is. Voli and sejuani are my mains in the top lane (Sej I just started maining about a week ago). I don't want to hear from people "Oh, well use this and this champ and he becomes a puppy dog." I want advice on how to defeat him, if possible, in lane as those champs. He seems the same as darius, literally unbeatable with a melee champ unless the darius doesn't know how to use him, except singed has infinitely better wave clear.
I will include that this was on a smurf account, so teamfights were shit, I can figure him out late game, but early game laning, his E flings you really far, straight into minions, it prevents you from farming at all while his q in my opinions is one of the best farming skills in the game. He just feels unbalanced, unless you're ranged.