Dragon Egg looks superficially similar to Nerubian Egg, but it's actually very different. Nerubian Egg is played in constructed mostly as insurance against AOE, as having a 4/4 after being consecrated is strong. It's also good as a target for argus and such, because it usually doesn't get cleared, but I don't think it would justify inclusion based on that alone.
On the other hand, Dragon Egg is pretty horrible if it just sits until getting AOE cleared, because then you only got a 1 mana 2/1, which is bad. I think the concept for that card is more to be a good target for buffs so that you threaten to spawn multiple 2/1s.
Dragonkin Sorcerer to me seems pretty bad except maybe in Priest. Yes, it seems intended to reward buffing. However, the problem keeping buffs mostly out of constructed is not that buff spells are weak, because (for example) Velen's Chosen is really strong in arena. The problem is that, in constructed, it's too easy to neutralize the buffed card efficiently via silence/BGH/class-specific single-target removal. You're punished for having sunk multiple cards' worth of resources into one card. Priest is an exception because power word: shield draws a card.
So I think Dragonkin Sorcerer's effect would be more helpful if it were to put an additional body on the board instead to give you something left over when it's removed, such as spawning a 1/1 instead of gaining +1/+1. That would be mostly worse than Violet Teacher though. So it's hard to see Dragonkin Sorcerer being run in any deck that doesn't already run Violet Teacher AND multiple targeted buffs, and I'm not aware of any strong decks like that at the moment.