Jays would need to do a lot more than Keuchel to have a reasonable shot at WC2 IMO.
The other reason for signing him and making other moves would be (1) to avoid having the Vladitos and Bichettes coming into a 100 loss club, (2) make TO more attractive as a player destination.
Keuchel at 4/80 is not too bad, most likely any negative value in the 3rd and 4th years would be minor.