Correct me or add your thoughts as these are preliminary ideas that stil formulate...slowly
+1

Up to this point Aether hasn't really introduced new decks as War has progressed; it's been variants of their original deck builds. This is for a few reasons:
1) they believe these are the best decks available to them (evidence: they keep winning), and
2) they have been able to fill up their losers because a) there haven't been many losers, and b) soooo much in-element salvage, and
3) it's hard to come up with new decks each round if you're already discussing/testing/etc 5-6 decks.
But notice that a high winrate is a part of
each of those. As their losses start to accumulate and they field fewer decks, they may start to venture outside the tried-and-true.
Especially if they are trying to counter a specific deck. So while I agree with everything you wrote, past performance is not a guarantee of the future.