The wizard will not see if the BM runs few bigs or Lair when its his turn to act.
BM runs to NC and wait with his QC till quickcast phase. It will be a lair or a ring/flower or even a forge.
But you wont get to cast a creature by then.
My personal list of possible threats I'd be reacting to in that circumstance is
- 2nd turn Pet Steelclaw and Cheetah Speed
- Lair
- Battle Forge
- Double Move + Ring into 2nd turn Wolf Pack (Redclaw and one or more Dire Wolves on later turns
I think we can pretty safely disregard double move + Mana Crystal from Beastmaster. If BM wants to try to build his economy, that just means Wizard plays turn 2 Tower or Forge 0and turn 3 Gate.
Against a 2nd turn Steelclaw, Opening with Jelly (or Golem) is probably the right play. If you start with Gorgon, you're probably locked into Gargoyle Sentry on 2nd turn to try to catch up on ground defense, but if you've got Eagle Wings for the Gorgon you're in good shape after that once you get Wizard's Tower up.
Against nearly all kinds of Lair openings, Gorgon is probably the right play, I think. Weak is good against medium threats, and the damage is good against small ones.
Against Battle Forge I'd suspect that Gorgon is correct, but I can't prove it. You may actually want 1st turn Gate to Voltari instead, here. But if you're playing Watergate or something similar, you're probably not too worried about the Beastmaster trying to solo you. You've got enough Dissolves that you can keep the threat minimal.
So, yes, some kind of scouting of the enemy spellbook is going to be important. In a tournament, that means control gets better as the day goes on and book play-styles are revealed. In casual play or league it just means learning your opponent's spellbooks and habits over time.
Then again, I may have a excessive regard for Gorgon in the current meta. She's no good against Necro, for example, and iffy against Warlock now. But against Beastmaster, I think she's still a tremendous play.