Honestly one shrek on your sturm squad is actually quite fine. as if you got two then you get super reps super fast, and this would be to powerful.
Two sturms are quite the investment but are worth it as well to push off mobilized assaults
Also your rektington is probably your best option on taking on tanks and light vehicles with your volk's snare. your AT weapons are really awesome, and grow extremely powerful to extreme satisfication when the penetrate a gaping hole into the enemies most precious and valued units
As I have stated before, good players support their vehicles with infantry (Allies infantry are beasts, let's face it) so when they see my SP or volks running up to get a shot, they will focus fire on that squad while reversing their vehicle, this makes it extremely difficult to counter any kind of vehicle play
The only effective use of raketens, from my experience, is to build 2 or more of them then either cloak-cap the map or blob them together to cheese enemy vehicles by volleys of ambushing rockets