AFC East Buffalo Bills Key Additions: WR Brad Smith (4 years, 15 million), QB Tyler Thigpen (3 years), MLB Nick Barnett (3 years, 12 million) Key Re-signings: CB Drayton Florence (3 years, 15 million) Key Losses: MLB Paul Posluszny (Jaguars), DL Marcus Stroud (cut), S Donte Whitner (49ers) Grade: C Why: I like the signing…