I see only Hertz now, too. Very disappointing, I used to make most of my rental car bookings via Destina and now the AC site. But with only one provider (Hertz) offered now, I will use another site that scans every car company at the airport.
This other web site (which shall remain nameless, I want all the good deals :-: ) - one time the gal at the rental counter said that my price was even lower than their employee rate (twice I have had daily rentals for a base rate under $20 CAD/day). At Discount and E-cars at their airport locations in YYZ.