Im not going to defend the performance of the stug IIIe but when comparing to T70 you also need to factor in tech-cost. You can build the StugIIIe without teching at all, it will then be alot cheaper than the t70. Still, for ostheer not to tech at all seems like kind of a horrible idea, so the "lower" cost is really not really there.
i know ppl will bring that building cost, but this unit is call in unit. if follow your logic all call in unit should be weaker compare to building units with similar price. is that truth?
guards, penal cost the same, guard is call in since it don't need tech does it weaker than penal? no..
shocks and pgren, shocks cost little less if u count Pgren need tech. does shocks lose to 1v1 fight with pgren? no... ppl might bring shocks cost more than pgren per unit with out think about tech and building, then that is my point, Stug 3E shouldn't under-performance compare to same cost unit.
mortar HT cost 120mp 30FU almost same cost as building mortar team, Mortar HT don't need building either does it sucks compare to Mortar team? no..
T34/85 is little bit more expansive than T34/76 but since T34/85 don't need building it is actually little cheaper, does it bad compare to t34/76? no....
so far i don't see any call in unit is weaker compare to similar price building unit in the entire game except this one. so i don't think "it don't need tech and build so it should suck" is a valid excuse for this unit under perform than similar cost unit
in fact some call in units is very strong for its price compare to building units
KV8 for example, it have similar cost of Panzer 4 and its counter part is Brummbar. Brummbar and KV8 are both AI tank, so KV8 should be weaker in AI than Brummbar right? actually no, KV8 have better HP, better Armor than Brummbar and it eats infantry squads like snacks. can the more expansive and need tech tank, Brummbar do the same? no it can't. how about compare to Ostwind? KV8 on its price is just little more expansive than Ostwind and Ostwind need building and tech. does KV8 perform crap compare to Ostwind? no, it beat Ostwind in all area except the mobility (Ostwind top speed 5 vs KV8's 4.8)
so building cost and tech price really shouldn't consider for the reason why this unit should suck because this is the only call in unit sucks for its price to be a call in