IMO, there's a couple things currently in play that lead to signing Gaffney: Deion Branch is on the decline, Welker may do exactly what Mankins did and end up sitting out 8 or more games, and guys like Ochostinko, Gonzales, and Stallworth may not even make the team. I believe after this signing, we will have 11 receivers in all including Tiquan Underwear, and we just drafted another receiver in the late round. Remember too that we signed Daniel Fells as a blocking TE who can break off for a pass here or there in the flat, meaning Hernandez will probably see some time as a wideout.
The one thing I thought we'd address in the draft (and maybe we did, because I don't know anything about Dennard and other late rounders) is addressing our return game. We haven't had a solid kick returner since Ellis Hobbs (Tate was okay, but very inconsistent).
The glut of WRs is exactly what we did last year with DTs/DEs.