Yeah, I get it's confusing as the "shock" stats are displayed as parts of 100 and the "efficiency" stats as 10. But basically a "shock" value of 40 will reduce efficiency by 4.
And even if the internal rounding in the game may show only 1 efficiency loss when attacked by an unit with 15 shock; if you attack twice, efficiency will drop by 3.
Especially when playing on higher difficulties, damaging the efficiency of enemy units becomes more important than actual damage to strength points. Some units, as the German Wurfrahmen, the Soviet Katyusha or the US Superfortress have "shock" stats of around 30-40. If you hit a Tiger-tank twice with those units, even a Bautruppe or Soviet conscript unit can finish it off. Even entrenchment doesn't really matter anymore then.
When playing, my first and foremost priority is to find and destroy all "artillery" type of enemy units ASAP. Flying or on the ground. Probably the flying ones first, though...
