There's a common thought out there, uniting optimists and realists alike-- "we have to have a huge haul of defensive linemen in this draft to compete." Regardless of your spin on this idea, it's unrealistic. No matter how many linemen we take, chances are they will not greatly impact this year.
Go to pro football reference and use their draft finder tool (it's quite easy) to pull up a list of defensive linemen from last year's draft. Take a look at the brief stats offered therein. It's quite sobering.
George Selvie was a seventh round draft pick. After three seasons of not much, Dallas invited him to training camp to replace injured players and he found a home, having a modestly solid year with seven sacks in fifteen starts.
Only one defensive lineman in the entire 2013 draft had more. In fact, take out Zeke Ansah, Barkevious Mingo and the freakishly successful run 6th rounder Chris Jones had with his 3rd team, and you need three players to match Selvie's sack total.
There's more to playing Dline than sacks of course, but the other numbers in the list aren't especially heartening. Only four players matched or exceeded Selvie's 6 approximate value points from last year and three of them were taken within the first 15 picks of the draft. Only five players started over half their team's games, and, again, three (the same three) were taken in the top 15 picks.
The draft will not fix this team this year. Our first pick is likely to improve the d-line immediately, if we take a lineman there. The rest of them, if we take any more, are not likely to significantly affect the line this year. Especially not those bargain sleeper guys you are thinking of grabbing in the fourth or fifth round. Those players are extraordinarily rare. It always makes me chuckle when people say the Seahawks showed the way by drafting Chancellor and Sherman in the 5th round. How simple. How easy. Just draft immediate impact, pro bowl players on the 5th round.