I don't think WR was what was keeping them from advancing last year. It was an underperforming defense at the end as well as injury decimination. I think WR issue has always been overblown.
In my mind what held them back last year was three things:
1. Injuries to key defensive players.
2. Lack of a real pass rush due in part to #1 and in part to a general lack of size / physical dominance on the defensive line.
3. Lack of truly dangerous weapons on offense.
Gronkowski and Hernandez in tandem made the offense unstoppable. Now, one of them is perpetually injured / ailing and the other is in jail. Back then, a really great WR wasn't needed for the team to be the best offensive squad in the NFL because of those TEs. Now there isn't a reliable pass-catching TE on the roster, so WR becomes a bigger need.