Targeting needs is something of a fools errand IMO. Rosters in the NFL change too fast, and rookies are seldom able to contribute immediately. Hell, half the early rounders won't even make it as NFL players.
Adding good football players is priority #1. You can use need to sieve between similarly graded players, but how many times has Dallas drafted a "need" player over a slap-in-the-face BPA player and ended up happy with their choice 4 years later.
I don't see a lot of "impact" prospects in the 12-15 range this year. There's some good football players for sure, but they're not guys who look like Pro Bowl game changers. If you think Morrison is a game changer, you pick him for sure.