Eric Ebron was not the perfect pick, but he was a good pick. At that point in the draft there wasn't a perfect pick left. Of course the Lions need a cornerback and an edge rusher, but they simply weren't there. The Browns reached wildly for CB Justin Gilbert, and the Vikings took OLB Anthony Barr the pick before Detroit. Without a viable trade option, no defensive player at a position of need that was left was a top 10 worthy player. Dennard, the guy all Lions fans were clamoring for didn't go until the 20's to Cincinnati. So if he was a guy that the Lions had to have, why did 6-7 secondary needy teams also pass on him as well? Clinton-Dix, Pryor, and Donald all were several picks after the 10th slot.
The NFL is about mismatches on offense, and that's exactly what Ebron will help create. In the slot Ebron is a nightmare, and the affect it will have on the rest of the offense will be very positive.