I reckon Wirblewind is a waste of resource against anything except conscripts and riflemen
If used alone, of course yes. But who sends an anti-air/anti-infantry tank with mediocre armour off on it's own? Supported by an IHT with two squads and a Marder, it forms part of a versatile and mobile little battle group that can be a thorn in the side of anyone relying on massed infantry and/or light vehicles. Combine this with an ally's Wehr armour or your own Panther group if you've got the cap and I reckon you'll be able to deal with most surprises rapidly and effectively.
The only things I see this combination being vulnerable to is (1) off-map barrages while doing repairs or point capture but if kept mobile the group should be able to avoid these fairly well too, and (2) groups of heavy tanks, but their mobility should enable a hasty retreat followed by a Henschel strafing run.