You have to consider the other guys too. Cooks not the sole WR, and your analysis doesn't include the PI penalties he draws by panicked DB's. Considering this, he's doing GREAT.
Those are numbers for Watkins, not Cooks.
Cooks to date #'s:
5/87
7/159
7/90
19 catches for 336 yards
No touchdowns yet but as you mention he has some BIG PI calls that have helped a lot.