This is the first Tier List since the recent balance update. As such, the Tier List is in an incredibly volatile state and is subject to drastic changes. Expect the Tier List to get more refined as results and opinions get more solidified.
Water finally rise to Tier 1. It's a very solid and (somewhat) consistent control deck that can very effectively shut down the Graveyard while also providing Quick-Effect disruption. The deck still has access to semi-limits and can fit the strongest tech cards like Loading... and Loading... .
The deck can adapt to every matchup in Side Deck format, and are only susceptible to a handful of counter-cards like Loading... or mass removal (where a single Loading... can't protect). Also, the deck is not that coin flip dependent, unlike deck liks Onomat, Triamid, or Noble Knights. As such, Water Xyz is expected to consitently perform in high-level tournament play.
Blue-Eyes is finally back at Tier 2 with the new balance update. This is mainly because their worst matchup in Desperado (with their auto-win cards like Loading... , Loading... , and Loading... ) got heavily hit to the point of unplayability.
With the rise of Onomat, decks like Fire Kings and Triamid raise representation, which also benefit Blue-Eyes heavily since they have access to Loading... and Loading... for the former and Loading... and Loading... for the latter.
Blue-Eyes currently faces two problems: their own consistency and Water Xyz's ability to consistently summon Loading... . Against Water Xys, Blue-Eyes usually needs first to prevent their set-up or otherwise open incredibly well to push through Dweller.
Thunder Dragons have risen to Tier 2 status. It has by far the highest ceiling in the current meta due to Loading... banishing Thunder Dragons from the graveyard triggering their effects, which gives the deck the ability to play through disruption. Previously, Noble Knights have been a troublesome match up for Thunder Dragons, but with the recent Balance nerf, they can't set up their strong boards as consistently as before. With the addition of decks like Cyber Dragon and Triamids re-entering the meta, Thunder Dragons have gained a lot more favourable matchups. However, the deck still faces consistency issues which have;t been solved. With the arrival of Loading... from the new box, the deck now has a way to completely clear a board including troublesome cards like Loading... and push for game with Loading... .