Let me start by saying that the disenchanting argument brings out some serious polarity in the Hearthstone community. Reddit's /r/hearthstone is known for having a major "just don't do it" stance when it comes to disenchanting cards. Their position is pretty solid in an environment where everyone has money to consistently throw at Hearthstone. That's not reality, though.
For those of you out there who play Hearthstone on a budget, or even as a completely free-to-play player, disenchanting cards is a viable and reasonable solution, especially if you're only interested in the Standard format, which includes cards from the Basic and Classic sets, as well as the last two years of released Adventures and expansions. That means anything before then is practically useless to you.
Nevertheless, some of those cards could be useful in Tavern Brawl and in other areas. I don't think it's a reasonable approach to just disenchant all Wild cards, even as a Standard-only player, but you should definitely open your collection and look over the least useful cards on the highest end of dust cost.
That's what I'm going to do for you in this article. After Journey to Un'Goro's release, we entered the Year of the Mammoth and a new Standard set rotation. If you only play Standard, here are nine cards you can safely dust. Please be advised that this list is relative only to the card sets that are leaving Standard in the year of the Mammoth: Blackrock Mountain, The Grand Tournament, and The League of Explorers.