hmm I would think the guard could make a counter attack since the counter attack is declared at the time they are attacked (which presumably would be before they are pushed)?  It doesn't seem right that they would only get the choice to counter (or be denied that option) after they are pushed.  I could be reading it wrong though.

P.27 Step 7
If the attacker made a melee attack on the defender, and the
defender has a quick melee attack with the Counterstrike
trait, the defender may choose to counterstrike the attacker at
this time. This is a “free” quick melee attack against the attacker.
The defender may counterstrike, even if the attacker’s attack
was not “successful” (did not roll dice because it missed or
was avoided).
The counterstrike attack is resolved like a normal attack,
starting with Step 1: Declare Attack, except that no
additional counterstrikes occur.

i did not play against this build. my initial reaction is that it seems like the spellbook cost is too high. out of school for 8 points is a lot. why not put in two iron golems instead and have 2 more  points to spare or for one more point put in the third golem. plus they are cheaper to cast than the grizzly.