For the worlds patch or worlds qualifier patch, you buff a bunch of champions that are already viable, but not enough to be played on the big screen. How exactly do you choose which champs to force stimulate here? It seems pretty hard to do this without biasing towards certain players/teams/regions Is there a strict method you use?
It's pretty simple. They just go on with patching for the game as normal in regards to item and champion balance. They tend to keep class updates to off or mid season. If a major overhaul was put live on servers right before Worlds (such as changes to Herald or Dragon), they simply go with the previous patch to avoid glitches, unbalanced elements that haven't been caught in development, and forcing pros to adapt to new elements on the biggest stage.
They are buffing tier 2/3/4 champs to increase the number of tier 1/2 champions.
Having a higher pool of top tiers gives a better diversity.
It's more effective than just nerfing tier 1 champs down, as the meta will still end up with just one or two above the rest, and just being permabanned. Or people just pick adc's in that role again. 
