This is true regarding the boundaries between Tiers 1&2 and Tiers 3&4. It is not arbitrary for between Tiers 2&3; the boundary is 50% winrate, nice and objective.
However, this “arbitraryness” is not a VS exclusive, it’s been part of the overall Hearthstone community, and the overall phenomenon on tier lists, for a very long time.
Perhaps most importantly, Tiers have NOTHING to do with ANY of the discussion on this thread prior to you bringing it up. Handbuff Pally is the best deck at top Legend as of the most recent VS report, regardless of what Tier you put it in. Technically, that report covered 8/14-8/20 so we’re talking about a timeframe in the recent past, but due to the lack of balance changes implemented since then, it’s safe to assume not much change, if any.
I partially agree and partially disagree with this. If players are rational, then they would use metagame information from other regions, researched through to the Internet, to inform their own strategies, to include which deck they choose to play as. However, this is a big “if,” and the answer to whether they do this or not isn’t really no, it isn’t really yes, the answer is “sort of.” In terms of whether it’s closer to yes or no, I think it’s closer to no, although it’ll always be some mix.
So yes, I agree here that separating data out by region would be a substantial improvement from the perspective of informed competitive play. HOWEVER, from the perspective of balance, I don’t think it really matters. Blizzard isn’t going to nerf a card in one region and leave it unnerfed in another. For balance purposes, combining all regions makes good sense.
Useless isn’t the word I’d use. I’d say contaminated instead. They introduce selection bias into the data, therefore increasing bias in the subsequent analysis.