The last major league debut from a first rounder from the Toronto Blue Jays was James Paxton, who owns a 71 xFIP- in 6 career starts with the Mariners after not signing with the Blue Jays.
The last signed first rounder from the Toronto Blue Jays to debut in the majors was Chad Jenkins, who owns a 111 xFIP- in 67 career innings. Jenkins was notably taken 5 picks before undisputed heavyweight champion of the world Mike Trout.