i started operation barbarossa with the same core force, i just updated my 5 P3's to the 5cm version and the P4's to the latest model and added 2 P1 flame tanks. i'll review in this post the 06/41-02/41 period of time.
the assault/advance missions were pretty easy since the tank force of the AI was only twice bigger. i found the assault missions pretty frustrating cause the AI brought tons of infantry (probably my artillery overbuy is one of the reasons :P ). the 45mm and especially the 76mm guns scared me more than the russian BT/T-26 tanks since the 1st sign of 76mm gun presence were my burning panzers. i avoided very heavy tank casualties by advancing short distances from cover to cover and if in open area i had to sacrifice some of my infantry when scouting without armor support.
my JPz's 1 and P3's slaughtered the poor BT/T-26 tanks aswell as some heavier T-35/T-1938 tanks. the AI used the KV's rarely on the assault/advance missions and if i encountered any, the only solution was smoke screen and then infantry close assault or my 88 guns mounted on trucks. i got some immobility kills on the KV's with my aviation and i even KOd 1 KV tank after attacking it around 5 times with my planes.
as for delay/defence missions: i think i had some luck in them since the AI almost overran me few times. in the 1st 5-6 months of the war the only guns that could handle KV were my 88's and my P3's with sabot ammo from close ranges so i preferred to employ my infantry and P3's inside forests if i had the chance and they made the KV's burn pretty fast.
after 3-4 months of play i came to the conclusion that my P4's are useless
so i sacrificed some historical accuracy and changed 3 of them to the captured pzkw B-2 740(f) (the french heavy tanks) and later i change the remaining P4's to captured T-34 tanks. ill use them until ill get the long barreled P4 in 1942
also in the process of this period i updated all of my 6 JPz's 1 to the better armored version of the same tank destroyer based on the panzer 38t.