I'm not crazy about any of the scouting sites, but it's not necessarily their fault. It has more to do with the system.
I like CBS for providing comprehensive listings of every prospect in easy-to-sort spreadsheet format. Like Kiper for being early. Like Lindy's and other mags (because they're mags)
But CBS doesn't get the rankings all that right. Kiper seems to feel obligated to justify his early rankings and downplays late risers and fallers. The mags try to scoop each other by hitting the newsstands early and ignore late trends.
Best thing to do: Watch a lot of footage, trust your eyes, read a lot of stuff from different sources and then compile your own rankings. Do this and there's less likelihood that Dak Prescott types will slip thru the cracks.