Hemet Nesingwary isn't exactly the best card in Hearthstone. He's actually known for being an example of a card that's simply too niche. Luckily Blizzard is giving him another shot in Journey to Un'Goro and while he's equally as circumstantial, it looks like he'll at least be played in very specific decks.
Meet Hemet, Jungle Hunter.
Destroying all cards in your deck that costs three or less is only desired in very specific decks. Aggressive archetypes need a good number of small minions to keep the pressure on and the slower control types can't afford to set themselves up to lose fatigue.
This effect very specifically benefits control decks that are aggressive in their moves, those that hope to win Jousts, and Holy Wrath Paladin.
What decks will you be using Hemet in?