A class action lawsuit filed in Washington Superior Court accuses San Antonio-based insurance giant USAA of skirting its responsibility to pay policyholders’ medical bills by using an outside vendor’s computer system designed to cut its payouts for healthcare claims. The plaintiffs — both USAA policyholders living in Washington state — maintain USAA Casualty Insurance Co. and USAA General Indemnity Co. denied their payments for medical treatment after they suffered injuries in separate car crashes. USAA officials had no immediate comment on the suit, which was filed on Nov. 16.