Darius: I think it's ok. Affects board immediately and needs to be dealt with pretty quickly. Should do well in a control/mid-range list. It has enough health to survive against many targets, and it'll grow to survive future targets.
Reddit comments are really down on this card, but I think it's going to be almost an "auto-include". We'll see, but cost is reasonable and the Rush+Effect are a strong combo.
--
Emeriss: We have seen so many Expensive Hunter Legendaries with AWESOME effects just never get played..... BUT... I think this has a chance.
I don't really see it in a Control List, which many will immediately think, because Control is so slow.
I see this buffing my Leeroy to a 12/4 and some charge minions, and many low-cost things that all of sudden have 2x attack and health.
The biggest issue is surviving till 10, spending a turn on this, and also keeping a decent hand size to take advantage. There is certainly potential with this card, but because Hunter can rarely meet those conditions, it may just be niche/meme card. I really think the biggest drawback is having minion cards left in hand to be able to use this effectively by turn 10. Hunters biggest threats are spell-based, and typically exhaust their hand early.
Stampede+New Rush doggie, or Cult Master, or Infest to keep hand filled are some ideas to keep a big hand size.
Cards from DK rexxar could really benefit from this too, especially if it's a "can't be targeted by spells" minion with another effect, you can lock down some games.
Dragon Synergy in Hunter will also be interesting. You have the new beast with Dragon Synergy card (Scaleworm), which I called garbage at first, but maybe fits here.