I dislike this compared to their old system as there's various breakpoints based on common toughness of targets, so s7 is much worse than s8 due to everyone playing t4 space marines.
But the system does seem like it can be useful if you build numbers around it, some of it's features...
1) Diminishing Returns and a Gradient built into it, higher numbers require bigger differences between Attack & Defense to reach the 2+ and 6+ points
2) This also means that the lower numbers have the biggest jumps, with every number difference important to attack and defense numbers of 3
3) Modifiers to the attack number roughly require 1/2 the modifiers to defense numbers to cause a difference
4) Can explain it as "greater, lesser, even, x2" which is straightforward. If you want to have cutoff points then it can be at "defense number is x3 higher (s3 fails against t9" or "defense number is greater than x2 higher (s3 autofails against t7)"
Now what kind of mechanic matches the flavor of the above? I'm thinking a To-hit roll where you compare melee skills ("My Melee 8 guy hits your melee 4 guy on a 2+"), and a to-hit roll where you compare Ranged skill vs a bunch of modifiers to TN (size of target, distance to target, speed of target)
You can also have "penalties/bonus to attack roll" and "penalties/bonus to defense TN" be specific categories. Maybe your attack roll only goes down or up with wounds and morale. There will be important breakpoints that people figure out and aim for but that impact can be mitigated somewhat by having a clear idea of where attack and defense numbers usually are.