I'm wary of the torn achilles, and he was bad last year even before that, but a lot of that can probably be attributed to the QB he was playing with. Depending on how much is guaranteed I like the signing. He's pretty much the only FA WR left who has any real chance at moving the needle, so if the guarantees are minimal then there's really no reason not to take a shot on him and see how well he can come back.
If we can get 800 yards and 6 TDs out of him I'll be plenty happy. He's not a WR1 anymore and his contract clearly reflects that, and based on that I expect to see more work done on the receiver front. Assuming the Pats and Gronk aren't already planning on a midseason reunion or something.
Could be a great move for Thomas, too. One year deal in a high-performing offense that desperately needs exactly what he offers, run by his former HC. If his goal is to get one more fairly big contract in his career, he has a better chance of getting 1200/8 and cashing in a year from now here than he probably did anywhere else. Just gotta stay healthy.