They haven't revoked a rework yet once it's hit live. They butchered Skarner and Cassiopeia TWICE and refused to admit they'd messed up. They gutted and mangled poor Morde, turned Fiora into an OP beast then nerfed her into crap again and I don't think they've EVER known what to do about Eve.
Riot just does things and sticks by them, no matter how many people hate it. Worst are the champs with small but dedicated fanbases who get reworked to give them more appeal overall.... only to end up dumped by the meta kids once they're not frighteningly OP. Those fans lost their favorite champ and for what? Two weeks of all the kids who spam whatever's broken playing them before they fall back into obscurity again? The people who already liked those champs get screwed to appeal to the masses. Fan of a champ? You matter less to riot than that guy who mains whatever the pros are streaming and calling OP that particular patch. It blows.
I was a big Skarner fan. He was my main ranked jungler for a season before his shitty rework made him trash.... then his SECOND rework made him OP as hell for two weeks before he got nerfed back into trash again. I feel for the Morde mains, because they did the same thing to him too. But Riot just keeps going on, doing what it wants without a care.
IMO the only truly successful rework they've done is Sion... and MAYBE Poppy. The rest are just various shades of meh or awful.