I fail to see a problem with a F2P deck making it to legendary. Aggro has always been the easiest path to legend, it's been true since the early deathrattle Hunter days. This is one of the most balanced metas I can ever think of.
Why do people continue to propagate the FALSE narrative that near-equal CLASS distribution equals balance?? THAT IS NOT TRUE. A balanced meta not only has near equal class distribution, but ALSO near equal DECK TYPE distribution. How many good control decks are there right now? How many good aggro decks? The meta is NOT EVEN CLOSE to being balanced. In fact, I'd argue that it's more important that the meta have equal distribution of deck type than class distribution. In fact, until recently, when people spoke about "meta balance", deck type distribution is what they were talking about, and not class distribution.