I think it versus Yeti is going to be a metagame call depending on whether 5/5's are common or 4/4's. If 5/5's are more common (And for clarification, that's 5 health or 5 attack, not both. So Sludge Belcher and Savannah Highmane), then you play Hungry Dragon. If 4/4's are more common, you play Yeti.
The key to evaluating which card is more powerful, then, is to figure out what you play when 4/4's and 5/5's are equally powerful, and I think the correct answer to that is still Yeti, simply because the summoned minion won't have summoning sickness, and that's a huge advantage from a trading perspective. You basically have to drop Hungry Dragon onto your own empty board, when you're at no risk of lethal so that whatever it drops doesn't hand your opponent lethal.
Anyhow, here's the full list of current targets:
That's 34 targets. I'd call it a loss with anything that makes it instantly into a 5/4, since nobody plays Lost Tallstrider and that doesn't even give your opponent versatility.
So that means that it's instantly a loss on 13 of 34 targets.
Of the remaining 21 targets, Blood Imp and Webspinner are almost definitely losses too -- Blood Imp would be a good card if you didn't have to waste a deck slot or a card on it. Webspinner is also good.
Mana Wyrm is a loss if they have a spell in hand. Lightwarden's a loss if they have a heal. Cogmaster's a loss if they have a mech. Undertaker's a loss if they have a deathrattle. All of those are reasonably probable, so I'd count them as reasonable probable losses.
So that leaves 15 guaranteed losses, 4 probable losses, and 15 wins, except even those wins are iffy.
Warbot on an empty board is bad, but if you have a 1 attack minion no your side -- say an Armorsmith or a Northshire Cleric, Warbot suddenly becomes a win. Goldshire Footman, Shieldbearer, and Voidwalker can all deny lethal. Any of the "wins" can easily become a ping on a non-empty board. Well, except Shieldbearer but still.
I think the Dragon Tribal is going to be fairly powerful, so that'll be worth something, but Mech Yeti has the strongest tribal in the game right now and it's usually the first card dropped from mech decks. Overall, this is probably the strongest card shown so far, and it's probably not good.