They come out in t4, unlike every other infantry unit in the game which comes out much earlier.
They cost 400 mp, which is more than shock troops and every other infantry unit in the game.
They come out at a stage in the game wherein vehicles that they cannot even hurt are on the field and likely vetted.
They're a three man squad, vulnerable to snipers or indirect fire that happens to gib a model.
A) T4 can be built second by OKW, for a grand total investment of 120 fuel. 180 fuel isn't enough for the Soviets to get a tank, and it's not even enough for the USF to get anything heavier than a Stuart.
B) Fallschirms cost more, Jager light are more to reinforce (Puzzlingly)
C) As for stage in the game, see A, I personally love to get Obers as early infantry to mop up die americane.
D) USF do not have snipers or mortars and the pack is a joke and, unlike weapons teams, mobile units are pretty able to just walk around to avoid all barrage fire forever
So yeah. At 120 fuel, I can throw Obers around, and all my opponent has to throw at me is infantry, and they are most certainly OP. Even when tanks ARE around, throwing obers around as a capping squad demands your opponent invest fuel just to counter your manpower, which draws their tanks out and leaves them vulnerable to pushes.