Introduction:
Dragunov has two high crush attacks, both low and both punishable. Inversely Dragunov has three low crush attacks that are safe but have low damage potential. While it's possible for Dragunov's crouch dash to go under most highs, there's so many faults with Dragunov's crouch dash that it shouldn't be your primary choice for close range, high evasion.
Why does he need more high/low crush?
Simple answer, high and low crush moves grant very strategic advantages both offensively and defensively. They can drastically reduce pressure that can be applied by your opponent, especially against characters that are high attack dominant (such as Steve).
The moves:
b+2 (high crush) - The first thing to notice is that b+2 leaves Dragunov in FC/recovering WS and the animation is of Sergei extending his hand out as he begins to crouch. The animation is of him basically instantly crouching, Dragunov is left in crouching, but his hit box isn't that of him crouching. b+2 being a high crush would allow it to be an ample alternative to the potentially unsafe qcb+2, namely lower risk for much lower reward.
qcf+2 (high crush) - Fairly poor tracking, fairly punishable on block (-14), and fairly long execution time makes qcf+2 fairly lackluster. To make things worse the damage potential off of qcf+2 is not much better than that of qcf+1 or f+1+2, both a full 4-5 frames faster. If anything qcf+2 should be Dragunov's hail mary/go for broke launcher, as such it should be his high crush launcher.
f,f+4 (low crush) - In DR f,f+4 used to high crush and low crush, this was countered by the fact that the tracking on f,f+4 is quite horrendous. Now in T6/BR, the move no longer high or low crushes, but it still has poor tracking. What's really interesting is that f,f+4 counts as airborne (therefore can be bound during the attack) even though it doesn't low crush.
f+3 (low crush) - Similarly to f,f+4, f+3 used to low crush in DR and inexplicably the low crush window has seemingly been tampered with. What f+3 would bring to the table is a low crush that can not be bobbled mid-air for a small combo. Couple the fact that there's two strong options out of f+3, on hit and block, would make f+3 an excellent move to have low crush properties.