Yes I was mainly thinking about the Malygos potential, which is close to 0 if it's a deck discount. But even without Malygos, I prefer to reduce my hand and have an immediate tempo swing the next turn than hoping to draw one dragon in the next three turns to have some kind of effect. The thing is, you wanna play this on 4 and play a big dragon on 6 after that. Having (for example) an Ysera that cost 7 when you have 10 mana is a lot less interesting and not worth a slot in your deck in my opinion.
As it is, I don't think this will see play. It's useless against aggro, and against control what is it good for ? Playing Ysera + hero power on turn 14 instead of just Ysera ? IF you drew this legendary first AND played it, which even though it's a 5/4 for 4 is a bad play. Nobody wants to play a useless 5/4 for 4.
Looks kind of ok on paper but the powerlevel of the expension is so crazy that I don't see how it's possible that this card could fit in a 30 cards deck.