The Cowboys former fourth-round draft pick is picking up the slack that Randy Gregory left behind. FRISCO – When it became clear last March that the Dallas Cowboys defense was going to lose defensive end Randy Gregory to the Denver Broncos, the team went with Plan B. On March 18, Dallas signed defensive end Dorance Armstrong to a new contract after he entered free agency in the offseason. The very next day, Gregory signed with Denver. Cowboys fans were panicking at the time, wondering how the defense could survive without their home-grown, seemingly former problem child, who was now possibly…