While it may appear that Clemson has a knack for producing mid-round picks, the average round that Clemson players have been selected has actually been steadily increasing since the beginning of this five year period:
As you can see, since 2009, the average round in which a Clemson football player has been drafted has improved significantly every year since Swinney took control (with the exception of last year, which I believe was simply a dry year for Clemson draft prospects with the exception of DeAndre Hopkins). A more graphic display of this recent trend:
Clearly the quality of professional football prospects produced by Clemson is on the rise (as illustrated by the descending purple trendline). With improved recruiting and increased national exposure, I fully expect this trend to continue moving forward. If you combine all of these factors it becomes evident that Clemson is slowly but surely becoming a football factory for the NFL.