6/6 for 5 faeria but health decreases by 1 for every enemy creature summoned, so automatically down to 6/5 next turn and it will keep going down… It’s not cheap either.
Exalted Ogre has 1 less attack but potentially +2/+2 for same cost. And it’s a common card.
A card’s rarity does not determine it’s playability. The card is bad, but “It’s an epic, and look at this common that’s better” is not a valid argument.
Crumbling golem is good to play to punish your opponent when they are low on faeria and can’t put to many creatures down. It’s also a unappealing target for a green player to hit because it does a lot of damage. As they summon more creatures it’s health gets lower and the green trade becomes less valuable. But green alao doesn’t summon a bunch of creatures every turn so it’s health will go down slowly.