https://vignette.wikia.nocookie.net/leagueoflegends/images/f/f6/Swain_OriginalCentered.jpg/revision/latest/scale-to-width-down/1215?cb=20180414203619 The reason how I climbed to silver so far is because of this champion. I don't understand why people don't play him, he is pretty viable.
He's weak. He runs out of mana trying to waveclear(since any other mage will shove him and roam), and has almost 0 kill pressure, while you have champs like 
who can 24/7 shove and never go manaless and whos numbers are so overtuned that she can actually take glacial augment over an actual damage keystone.
idk beats me people would rather pick 0 cc laners and beg for ganks and lose.
he has a solid kit and hes potentially getting a big buff to his ult in terms of usability and extremely good items for him.
He's been nerfed a lot and his kit relies on people getting hit by W/E so his R hurts, higher ELOs that doesn't happen as much and low ELO often doesn't bother learning Swain since those are tricky skillshots and they rely on easier champions to carry.
His kit is generally unreliable but when he pops off he can nuke a whole teamfight.
Because hes a mid-range scaling champion with no mobility, the only late game he has involves building a tank item or two so he isn't oneshot deleted since his only survivability is a health steroid on his R and subtle (but consistent) healing through his souls and R drain.
He can be strong once he gets full build and in group fights....but like others said, his waveclear isn't enough to reliably get him there while his team runs it down one by one all dieing.
He's been garbage ever since they gutted his ult because he was strong during the mage botlane meta. His ult wasn't even the problem of why he was strong, but they nerfed it anyway.
