To me it seems inefficient. Why not just tweak numbers if their current kit is UP or OP or broken? Is reworking a champ really worth never being able to play the original one ever again? Lots of champs that were reworked may as well just be new champions, they could have left the old ones in the game.
That doesn't do much about dealing with kits that straight up aren't healthy. Old Sion is a good example, for all that I loved him.
He was purely binary - either he did well and ran the game or he did poorly and was a non-entity - with a hugely non-interactive kit. He could be fun to play as, but was never really fun to play against. And tweaking his numbers would do nothing more than determine where he fit in terms of power - either he'd be too weak to matter, or strong enough to be dominant.
The numbers were never the problem with Sion. The kit itself was.
