Here are the correct 2014 numbers
Haren: 1yr/$10m, 32 starts, -0.6 WAR
Santana: minor league contract, 0, 0
Johnson: 1 yr/$8m 0, 0
total: 2 yrs, $18m, 32 starts, -0.6 WAR
All 3 bouncebacks were contingent on improving health, which is a horrible gamble with significant risk, esp. when guaranteed a roster spot. Likewise, Masterson's coming off a knee injury and decline in velo, and he'll require a 25 man spot to sign and guaranteed money, etc. Morrow made 6 starts and struggled with a forearm injury, and will also require a 25 man spot. Horrible gambles.
If there were bounceback candidates that were perfectly healthy and due for statistical regression (as with AJ Burnett) or were identified as change of scene candidates (as with Hughes or Liriano), those might be worth pursuing -if not for the fact that there are at least 4-5 front of the rotation arms who logged no DL time last year and were extremely effective.