+4 is actually good:
Dragunov's true weakness are generic d+1 low pokes. Depending on how much you've played and possibly who you've played, you'll find that generic d+1 is a really fucking good counter to Dragunov's +frame moves. Since Dragunov's u/f+4 combo nerf from DR to T6, Dragunov no longer has a threatening low crush attack. Therefore the risk versus reward to do such a generic s-mid is actually pretty good. Then low parry you say? Well that covers panic s-mids and lows, but that won't actually help you against panic mids and hop kicks. For instance, let's say you get a blocked iWR 2, +4, you opt to do d+2 (i18) to stop SS/SW, instead the opponent decides to hop kick (i15, i10 to get off the ground) so even with your +4 the opponent "beats" your d+2 by three frames. Now what happens if you think they were going to low poke and low parry instead? Same result, random hop kick is going to full launch you.
That's the problem with +4 on block, there's too many options that can be used that will beat out you out every time. So unless their back is directly to the wall and you're left beside them, assume that whatever you're going to follow up with is going to fail.
d/b+4 is actually good:
With the exception of d/b+1, there is no thing as a good generic attack. With frames that are usually negative on hit, to worst case scenario are launch punishable on block, generic moves are relics of laziness and can be dealt with accordingly. If you refer to my "Countering generic low spam" article, I already talked about why a generic low (such as d/b+4) can be easily dealt with, even on hit.
d+3 and FC d/f+3 are good moves:
Don't get me wrong, d+3 and FC d/f+3 cover two niches quite nicely, namely two long, invisible lows that can hit grounded. Even though they are the only two options doesn't mean the moves are fundamentally strong.
Problem 1) Both d+3 and FC d/f+3 are negative frames on hit, while that doesn't sound like that much of an issue, this can bite you in the ass if you don't remember during a match, especially during a high pressure situations when the opponent is more inclined to panic hop kick.
Problem 2) This ties into generic moves being terrible on hit and block. Just because an opponent doesn't properly punish a move doesn't mean the move isn't punishable. Both d+3 and FC d/f+3 are launch punishable on block and while people will usually not punish either properly, don't assume it's never going to be.