Whats supposed to happen is they change the champ so that its viable, and fun (hopefully in the way it was fun before) unfortunately thats not always possible.
Like with Evelynn where they kept parts of her ravage there, replaced the magic/armor pen for an attack speed steroid, now two attacks, watchout for that stun.
Her hatespike that although better for laning and damage no longer applies on-hit affects such as madreds, nor does it detect invisib;e champs as viable targets when it should.
Gave us her speed buff and passive to replace the funner huge invis that made evelynn so much fun to play regardless of viability.
And they shopped out the heal from kills, assists, or being close to the person who died for an AoE nuke that just like her invis is too OP to let her keep, but instead they slapped it on, kept her increadibly weak in all other regards.
no true invis(she just impairs other peoples vision slightly) yet still treated as a true invis champ (invis champs get to be weaker in every regard because they have invis, the counter to invis is the eye, the eye doesn't work on evelynn because her invis runs out before it will see her, clearly her invis is superior and too stronk, better make her squishier to compensate).
BEWARE THE REWORK it could happen to any champion, ANY of them, you love teemo? well his mushrooms are volatile to fun, we'll replace poison darts with the same thing but double damage and it only affects minions so that we can compensate for your invis which now works like Eves, but you still can't move, your mushrooms aren't invisible anymore and have a casting time of 5 seconds. There, teemo is now fixed, but we'll be tinkering with that MS steroid, i think you need an AS steroid instead.