What exactly did you mean by killing power then? Because it's killing power isn't any thing special compared to other light artillery.
It's got green cover because it can't be used behind shot blockers and be effective, you need to sit it on an open field/plain. And the clustering of the gun crew can be a blessing and a curse. It's range is also good to off set the fact it's AoE is relatively small compared to that of other light artillery pieces. In practice you won't be using that full range that often either.
Depends on an insane amount of factors from map, to cover, to truck placement to range of engagement ect.
Welcome to every other light artillery piece in the game hombre.
Similarly with the ISG you need to move it around because shooting at max range won't get you very far, mortars can use shot blockers and whatnot to their advantage. With the ISG this is the opposite.
It's useful for shooting at emplacements or buildings, but it's so insanely buggy using it to shoot at infantry is just gimping yourself.
If anything it needs it's vet fixed. Not a nerf.
EDIT: Can we like stop trying to kick OKW in the balls in 1's and 2's just because something might be to good in 3's and 4's were you can spam it.
by your logic then the old 120mm mortar was ok...
this unit is too good for its cost and can win a game by itself(assuming you can protect with atleast 3 volks squads)