You actually answered it urself! player invest his mp into squads as soon as he has manpower for it! that's the thing, since OKW teching is very cheap and the factions doesn't generally give u options for various support weapons such as mgs/mortars etc you build another (very cost efficient) squad (which u can upgrade it to the mighty shreck).
OKW stays broken as long as it's easy to shreck blob, or shreck has such a performance
You are really not playing this patch otherwise you would have noticed a few things. 1 the okw tech cost got increased by 50% when it comes to mp . vg's have their mp increased. thats one vg squad less. and you are correct in the past the okw could not invest in anything but vg's. but the latest patch has me pushing for the luchs / puma combo. so thats 3 whole vg's squads you will not be seeing.
as somebody already said shrek blobs are really bad when dealing with infantry. and shreks are really not as usefull as out make them out to be.