I don't know this for a fact, but I get the sense that many GMs rank players in groups of comparable ability (high R2, mid R2, etc.) vs. a pure force ranking (e.g., #38, #39), and if there are two players with comparable ability but one plays at a position of greater need they take that player. A player who drops far enough where they are ranked better than others would be the pick (or you trade down if you really don't need/want them) -- I would assume that's how they ended up with Rodgers and Lacy.
GMs that absolutely love someone at a position of need and trade up for that player (CM3) would logically only do so because they think there's value in doing so. I think that's different from drafting purely on need when you're on the clock because you're actively making a trade to get a specific player who you think will fit vs. letting fate decide who's the best 3-4 OLB left on the board.
Maybe that's a long way of saying that I agree that teams combine both strategies. There's no way TT drafts 9WRs. TT tilted towards need on his picks a bit too much on 2012 (the infamous all-D draft) and he's been rightly roasted for it.