I believe that Russia building Artillery should be a break out maneuver. If you have the units in Caucasus or Russia and the Axis are not very strong, a one round build of 6-8 Artillery (assuming you have the cash on hand to afford that many) can significantly increase your offensive punch while not overly effecting your unit count. (Sure, 6 artillery is the same cost as 8 infantry, but it’s only two units you are short. Meanwhile, assuming you have a large stack of infantry; and you do, don’t you?; it’s increasing your attack punch by 3 for each Artillery) may convince the axis to back off instead of pressuring your further.
Honestly, however, I see it more often used in Germany. Germany gets a bad defense in W. Europe, the allies throw units in, Germany fails to liberate it, and next round they have a stack of infantry and fighters, but buy artillery. That way they don’t have to pull back tanks just to kick the allies off W. Europe.
Just a scenario I thought of. I’m sure there are plenty other similar scenarios you can think of.