His 2015 was his best. For sure. In fact he was probably a better runner than receiver. At least one of his receiving TDs was really a run (short shuffle pass/handoff from Foles vs. Green Bay).
But the sum of his work in 4 years just doesn't impress. Yards from scrimmage? 79th since he came into the league. Punt return average? Bottom quarter. His catch % (among anyone with 150+ catches)- bottom third (which is pretty amazing for a guy that has so many screens thrown at him).
Other than 3 highlight reel punt returns he has just not been an above average player. He can and should benefit from better and more creative coaching on offense. I really think he will.