Riot What is your aproach on meta champion rotation?

When you nerf a champ or buff a champ what thought process do you follow? Since the meta is created either by what is left out of the pool that has not been nerfed, by champs that are new or champs that have been recently reworked, Aside from champ rotation what is your goal? When adressing a Healthy gameplay what things do you take into consideration? I see a lot of the pro play and some champs that are just broken in the correct hands but instead of adressing the issue directly the champs get gutted and rotated then reworked in a cycle that gets boring. Lee Sin, Riven, Zed and Vayne being the exeptions to this rule due to the High player base leaving them a bit weak but not too weak to keep them alife and to keep people happy. Is that healthy on the long run? While their kits are unique are they Healthy? I enjoy the game a lot although things sometimes get weird on those nerfs and buffs.