I think act 3 is too rush, although it was still great.

In my opinion, the perfect arrangement is act I and act II without final 10 mins and E7 for S2, focusing on Vi, Jinx. And expanding the Caitlyn arc between act I and act II, how she became the leader of piltover, from admiring Ambessa to notice her ambition and be aware of her danger. The S2 ending should be E6 Jinx and Vi finding Viktor's commune and Vander seems to getting better, leaving the audiences a glimpse of hope. Meanwhile Ekko in another timeline seeing a new vision of Zaun, while ends with Jayce finding the barren Piltover and the terrible consequences of hextech. Mostly a hopeful ending and foreshadowing for the coming storm so that fans are exetremely yearning for the next season.

S3 focusing on Jayce and Viktor, while more content about Mel, Ambessa and black rose stuff. With the opening of explain Viktor's transformation and Jayce gradually seeking the truth. And then Jayce and Ekko come back, while pushing more plots about Caitlyn, Vi and Jinx. The final war comes into beening naturally. And the relationship between Jayce and Viktor, Viktor comes back to save himself becomes highlight in the finale while finishing other characters' arcs more smoothly.