I posit the key lesson: it's often ineffective to use targeted nerfs to fix widespread and determined power creep.
I counterpose that that was never the intent, nor it is a desirable, achievable or realistic goal.
Late reply, but... I think the source of what people are complaining about when decks get out of hand is a massively inflated baseline power level in Hearthstone. Once this is the standard, a high power level makes anything close to balance almost impossible. Healthy and interesting metas are the exception rather than the rule in the past two years of Hearthstone, and that's probably coming directly from the extent of power creep.
I don't see power creep as a problem in terms of protecting value (HS isn't an investment, it's a subscription game), but that this kind of unbalanced meta, combined with the fact that decks have to be razor honed and focused, just makes the game less fun. Opponents are all kinda samey, playing netdecks. But folks have to netdeck and not experiment, since decks that aren't at that level get severely beaten.