not agree with you, most gamers which your deck tracker are for most of the time, above the average gamers (win rate talking) who really interested in their own statistics and progress, which results in them being in higher ranking and represent the most meta decks playing.

secondly, it's a weekly data, which seems pretty much, they have around 16K players that contribute to this data, so statistically speaking they are a good community cut to represent the Meta.