Remember to consider other factors.
Stationary or moving.
Vehicle or foot. (Grunts get better protection in rough than vehicles)
Type of fire - direct or indirect. Cluster or flame or HE or whatever.
Up hill or down dale - a tank on higher terrain tends to be considered at least part hull down, and so receive more turret hits than hull. (That may be bad for Pz4s with the thin front turret.. but that was true IRL)
And - no there is no "integrated table of protection values" - it is spread throughout the code, so even I could not really state one way or the other without a detailed read through. Which I am not going to be doing.
A HE round going off in mud, swamp, lake, snowdrifts, river, soft sand or volcanic sand is deemed to be impacting in soft stuff, and has a slight HE kill deduction. But not if cluster.
Soft sand
is dunes (it has a height component over plain desert hexes). Volcanic sand is really peculiar to Iwo Jima, and a very few other places like it. Both are somewhat horrible to operate wheeled or less so, tracked vehicles.
Me - I tend to gravitate to rough terrain hexes
esp those with a handy friendly or enemy supplied shell hole. Guess what type of hex I look for in my rear zone, when deploying my mortars or howitzers?
.
Cheers
Andy