Hearthpwn

 It's true but that rule does not apply to common and popular minions such as Azure Drake and Defender of Argus that are arguably auto-included in some decks so it really doesn't matter if Polluted Hoarder is balanced, I believe he needs 4/3 or an additional effect in it's deathrattle (not double drawing cards) or it won't be able to contest with other cards these I mentioned them, Azure drakes acts as a 4 mana ogre with additional drawing card and perhaps it's balanced but strong while Defender of Argus can get 2+/2+ with double taunt which is too good for a 4 mana and can be good at late game too because of large minions can also get taunts later on. Polluted Hoarder is actually unplayable because as a 4 mana minion, 2 health is way out of place (same thing to magma rager but ice rager is actually playable for appriopate stat of 3 mana cost minion) 3 health would be the least to play for any 4 mana minion unless they have good effect like corrupted kobold. Same thing to Core Hound.

So there are 3 details I knew about it: Each X mana minions the health should be appropriate like the basic cards, example is Windfury Harpy because 5 health is the least for 6 mana minions (still bad though) but Justicar can be accepted because it has good effect. Another example is the least 4 health Anubisath Sentinel is actually playable because the health is minimum to play for 5 mana minions. Second, competitive cards must be made like example that plays as X mana minions but acts it has more valuable or synergies well example. Violet Teacher over Chlldwind yeti for spells and Sludge Belcher over Fen Creeper, Any 10 mana minions over Faceless Behemoth, seen that all cards are neutral? Third, Blizzard is bad at balancing (atleast they are very creative) there are 35 new cards are not used on ladders, Even there's a new 7 mana card with 5 health and a windfury, is really unable to play it even in casual. Polluted Hoarder won't be able to contest of course but it's unplayable too. So think about it, some cards are too useless and some cards are not better compare to overused cards, we just have to accept it and hope blizzard make it all cards playable even it is bad on next expansion. This card only works with Forlorn Stalker and it is too slow to help N'zoth in the game.

TL;DR This card really disheartened me after I played the game when I added this card to my deck blindly. The card is out of place because the health is too low for 4 mana cost. If you played this card, it  will waste your plentiful amount of mana. No question, just dust it.

It still would be a poor card except it can be playable, the 2 health minion for 4 mana cost is unreasonable to play this card, anyone would concede the game instantly, if anything summoned it. Core hound and corrupted hawk is an example that makes the card unplayable because of extremely low health to waste 7 mana on it.