Without context, the signing of A.J. Burnett looks like a coup for the Phillies. They signed one of the top dozen starters in the National League from 2013 to a one-year deal that, at $16 million, doesn't overpay based on his recent standard of production. Burnett is 37 years old and has had injury problems earlier in his career as well as a reputation for an unwillingness to play through pain or discomfort that he has disproved in the past few seasons. He was worth 4 Wins Above Replacement in 2013 (using Fangraphs' version, which normalizes BABIP), 3 the year before, and even at that level would represent good value at $16 million.
Context is everything, of course, and the Phillies aren't the right team to hand a 37-year-old pitcher a one-year deal unless it is with the idea of flipping him for long-term assets at some point during the season.