It's a little blurred but its a 2 mana 2/2 with deathrattle into 6 mana 6/6 with deathrattle into a 10 mana 10/10.
So basically a creature card that can be summoned three times. It's cool in practice. If meta changes away from Pirate aggro and decks that attempt to play their hands quickly then would consider this.
Tempowise it's weak, but I wouldn't call it bad. It's a control card, that allows you to build your deck a little bit differently, allows you to put a little bit more removal spells and acts as a curving out win condition in some sorts. Quite interesting card.
Did people miss the new "Elemental" tribe? That means that this card will have synergies. Only 4 cards have been revealed so far. Personally, I believe that this card will show some real potential after more cards are announced.
2 mana 2/2 with an effect is considered 'bad'. We already have a 10 mana 10/10 that's considered worthless. A 6 mana 6/6 isn't that useful in any meta.
It's just a bad card. Though note that it's one of the first reveals of an expansion. We tend to see the worst cards in the set show up at the announcement. I cringed HARD when they said "mage legendary" being shown off now as I knew it would be bad and...there we go.