Land mattress always has been a huge source of frustration to me, it's cheaper and much better than stuka, and going stuka to counter it means I won't have fuel for Schwerer until late game. Not to mention even if I wipe rocket lanucher's crew they can just pick it up again, it wouldn't work if the rocket unit would be a vehicle... In my last 2v2 game we got rekt by usage of huge british blob + double land mattresses, blob with piats ate our tanks and land mattresses firing phosphorus and usual rockets rekt our infantry. Any tips how to counter such thing as blob connected with rocket spam?
could always go heavy on the infantry as they are blobbing, try mg34s and other suppressive types,
going breakthrough for the g43 fuzz, to keep up with heavy infantry opponents. just don't get the commander if you aren't willing to baby sit him.
also, if you feel like you need AT get you shrek upgrades with your sturms and get a raketen, two if you can micro them well enough.
also piats aren't really great vs infantry so you will start getting the advantage as you keep vetting. if you feel like you are going to get hit by arty a lot, just remember not to let your units clump and keep your squads spread enough to support each other but not enough to get hurt by explosions.
other commanders
luftwaffe the falls really tend to hurt especially once you get your smoke nade. and can chew up infantry. just remember these guys can be super squishy.
Armoured try getting a puma for heat rounds and let that carry you untill you can get your jp4. the jp4 can handle almost anything british launches at you. and well sturmtiger for le bloberino
spec ops, the flares are super helpful to know where your enemy is, as well as it will help with accurate barrages. also the hide from the minimap ability can be strong.
overwatch is kind of meh, but if you can get a good goliath off you are more or less set on game.
and for the fire storm commander, the salvage is really good, and the flame throwers on sturms are really good too. and the before your engagements and when you have enough munitions use the manpower ability to help recoup your losses. this ability is what makes this commander good.
and as for your recon, ostwinds can chew out infantry very well. just baby sit it please, as for the scout squads try to not go over board on them, and let your volks take the hits while your sniper squads do all the hurt..
that is all i can think of. and i hope this helps you form new ideas.
(flaktrack is ok, but you will have trouble with piats. and the ISG would be ok, but you have to micro that hard as well)