"Eve doesn't deserve to be viable, she's toxic so i understand why Riot nerfs her."
This is a great example of people having their own opinion of how things should be and how often that differs from other random players, let alone Riot. So often the forums are a hotbed of echo chamber, group think, upvote farming, win rate touting (as if it matters) utter garbage repeated by idiots who are awful at balance. And that's from a fellow hater of Riven who wants to see her nerfed into oblivion. Riot's not perfect, but they're WAY better at balance than the forums give them credit for and obviously way better than the average forum goer at it.
EDIT: To be clear, I'm not saying you're doing those things. But the forums in general do, and I'm sure you've seen the end result of it.
My own feelings on the champions you mentioned just for your pleasure so you can contrast it with how you feel about them and see what I mean:
I don't think Eve is toxic or should be made unviable (and neither does Riot from what I've seen). But that's just my opinion on the matter. I've only barely played her, don't play against her that often, and she seems fine in the high tier and pro games I watch. The latest PBE nerf seems a little unnecessary to me but not that big anyways. Oh look I just checked and the latest PBE changes include reverting that nerf. PBE is PBE.
I agreed with Riot on the energy return change for Lee as a fellow Lee scrub (I don't even own him). The ult buff seemed tiny but not really needed. Overall a pretty small impact, especially at high tier play.
Galio is a weird situation to me because I think he's actually quite good. However he has kit issues that make him a little worse as skill and coordination of the enemy go up, making it very unlikely for him to see high tier play. Also he's really hard to play well, especially early on because his mana is rough at first. Combined these two factors leave him in an awkward spot where he's OP at low tier play but only in the hands of people who main him. But if Riot makes his mana less of an issue in the early game he gets really annoying to play against for lower tier players. So how to change him? And does he really need changes? I'm not sure he does. They did in fact buff him twice this season as well, though not greatly. I could see his E costing 60-80 mana instead of the 70-90 it does now though. Currently using it early at all is usually a mistake.
I don't think Vayne is a big problem right now. I know the stats. Blah blah stats are skewed, partially self perpetuating bs anyways. The main thing is Blade of the Ruined King is too good and Vayne is annoying to deal with. I think if they just cut the stealth on her ult + tumbles in half and nerf BotRK a little she'd be fine. It's hard to cc her when you can't see her.
Shen was a little too good. I think they're trying to make his laning and split pushing a little less safe as well as take away some of his hidden power in team fights. Seems reasonable. He got some hefty buffing earlier this season and has seen a lot of pro play since.
As long as they're done right I'm ok with some Syndra buffs. They just gotta be real careful. Her mid game is good and with all the bug fixes a lot more consistent now. I wish her play style was a little less binary but whatever. And that's from someone who currently gets facerolled by Syndra. Man I gotta learn how to play vs her better. If they buff her enough elsewhere they should increase the cd on her ult a little, it's rather low for a point and click nuke.