Avaricious Dragon is no Stormbreath Dragon. As a mythic rare Dragon, he seems rather lacking, as his card advantage is instantly negated by the requirement of having to discard your entire hand at end of turn. Outside of being useful in top-deck wars for Red Deck Wins, the Avaricious Dragon definitely can end up wasting far more than it wants.
From a flavor perspective, this guy makes plenty of sense. He's not a bad core set Dragon. A 4/4 flyer for 2RR (2 colorless, 2 Red) is perfectly reasonable, but having no haste and a card advantage mechanism that will only be worth it in pure top-deck mode isn't worth a mythic status. It's one of those somewhat too good to be rares that plague the mythic rare slots of many sets.
Now in a Dragon-centered metagame, it's not so terrible. There is Dragon Tempest, the Enchantment that would not only give it Haste, but also deal 1 damage upon its entrance. Thunderbreak Regent will help it from being instantly removed with its punishment for removal spells being played against any of your Dragons. I just don't see Red Deck Wins wanting to play this over the Regent or something like Ashcloud Phoenix.
It's probably playable, but it's not hard to understand why players are so disenchanted by it. There are already so many powerful dragons that have been printed in recent sets, so I get why Wizards R&D decided to tone down the power level a bit for the Magic Origins mythic rare dragon. It still may be better than people think.