I agree to all of your points, i prefer long campaigns, a growing core force army, and so on. To be honest, the option to develop a coreforce over the course of many DLCs is one of the reason for my tons of diffrent playthroughs since release. But i like small scale missions aswell. For example the battle for stalingrad would have been great (for me) if it was a 4+ minicampaign in 42.
My reason to buy that DLC is, that maybe in the future there might be a combination of a big DLC series that contains "minicampaigns" on nice theatres of war foming a real huge! campain when its finished. So my approach to this is"let em tryout stuff"
But ofc that is my wish/hope for the future.
A more reasonable point for me is:
Its PC2 singleplayer campaign content in a nice and interesing theatre of war. Even its a little smaller, im pretty sure i will have a lot of fun with it and enjoy it while im waiting for the next DLC. So its a surebuy for me.
But just as a reminder, im the fanboy that would buy the "Landcruisers vs Godzilla" DLC aswell. Or a zombie-theme flavour DLC. (zombie tanks!!!)

It could be way worse, imagine being a Battlesector (great game !!) pve player...no story driven campaign content since release of the base game.