Once the patch hits it'll be severely gimped. Guards won't be able to snipe models, 120mm is tolerable. That just leaves rushing the 85's which is rather pointless.
It still has amazing synergy. Mark target to kill tanks, guards to counter light vehicles, heavy mortars to punish trucks. There really isn't a downside to taking it when facing OKW unless you are a dumb dumb and he stuka's all your troops.
It's never been that Guard motor is literally christ incarnate in a doctrine, it's just that it's very straightforward to use.