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So far, this opening with 3a was a fast enough response to early aggression. Once it will fail me, I might change it.
In my local meta, turn 2 aggression usually don't deal enough damage to seriously threaten on the 2nd turn, but is a beginning for a more serious aggression on the following rounds. Against such aggression usually the panzergarde+defend on turn 3 is enough, and the goblin grunt is a 3 dice attack until my opponent take an action to get rid of him (which is an action not spent on attacking my mage).