Remember sky golem? This card probably won't be played in top constructed decks. It's not like mage has lacked solid value minions in the 6 slot in the past. Maybe the meta shakes things up enough, but so far looking like an arena card, or a budget value deck.
Sky Golem is actually a good card for 6 mana. Its just in constructed its not good enough.
#1 it has deathrattle meaning it can be silenced or removed without giving you value.
#2 it was a mech and most mech synergy decks were aggro meaning this card rarely fit in constructed decks.
#3 its an Epic so its not seen in arena that often, but when it is its a good card.
Like just imagine how annoying arena would be if every game you had to deal with a sky golem... that would be annoying as shit.
The new mage card gives you immediate value and you have the chance to chance multiple in your arena draft quite often. Pair that with it being in the class with the best removal cards in the game and you're just asking for trouble.