In my experience using a 4-3, your pressure comes almost exclusively from your LE and your linebackers, particularly your LOLB. I've got Devin Gilbert (again) in my current franchise, and in standard zone or man cover packages he's not very effective as a pass rusher - and with his stats he should be.
Your DTs tend to penetrate on 4-3 line-slant zone blitzes - there are a couple of plays that, naturally, not every playbook has, where DTs tend to arrive in the backfield very quickly. The problem with Gilbert on these is that he's "too fast" sometimes - for example, he'll start off over the right guard, but by the time he redirects he's crossed all the way behind the center and is blocked by the left guard.
For those in the English path, Patrick Lopez and Julian Wilson are better fits as DT zone-blitzers because they don't overshoot that way, and they
will hold the point-of-attack on standard plays.