That's why the Tiger and Panther for example havn't been direct answers to the Soviet T34. Both tanks have been in production since the late 1930s, the appearance of the T34 has speed up the work a lot though. The german heavy tank program was started before the war to eventually counter heavy tanks of enemy nations. Though experiences from 1939 and 1940 gave the German military a false sense of security. Their success was more of a tactical advantage than in equipment since both France and Britain had at least equal if not even superior tanks on the battlefield, so many saw no real need to rush those new designs in combat believing the Panzer III and Panzer IV designs would be more than enough to deal with any threat, this idea as wrong though and many German tankers payed that price in fighting the Mathilda 2 in the African desert and the T34 in Russia. But the Germans deployed their tanks in a much more sophisticated fashion early in the war, utilzing speed and modern tactics which are even today trained on military academies, in modified form. As forcing the fight on the enemy and speed/mobility still beeing one of the tenets of modern combat. As far as the war doctrine of large armies is concerned.
Besides, Many believe the Germans in WW2 achieved their success due to their superior equipment and training of their soldiers. while the Germans did deploy units with very good training and adequate eqipment, infact that is only half of the story and those units made only a small portion of the army. Most of their success was on a tactical and strategicial level, with experienced field commanders and generals deploying modern tactics and concepts. And most of the battles the Germans won which was early in the war, like against France or the early victories against Russia, have been achieved actually with inferior equipment. And the training of the common German soldier was not that sophisticated if directly compared to their enemies, most of the larger nations around Germany had for example superior tanks, at least France and Russia deployed heavy tanks of which Germany had none before they decided to deploy the Tiger in 1942 for the first time, and it was never really a very common tank even after full production in 1943.
The British even captured a Tiger in 1943 in Tunisia, and they correctly deducted that all of their current designs will require comletely new ones, however they had neither the time nor the resources to make that happen. The Brits responded to the threat with higher productions of their high velocity 17 pounder mounted on different kind of vehicles either as medium tanks, like the Sherman resulting in the Firefly or tank hunters, like the Achiles and Archer. And those vehicles have been very succesfull filling the gabs till better designs like the Centurion, Comet etc. could be produced. The US simply neglected this, even though they received warnings about new German designs from the Soviets. There are probably many reasons for it though. Maybe the production of their 76mm and 90mm anti-tank guns would have been speed up if they saw a bigger threat in German armor. However one should not forget that the US had also many different problems to deal with, like the logistics. Those played definetly a role as well.
Like I said, it is not completely illogical to think that the Power armor would see quite a substantial number of different designs, maybe even as something mundane as field conversions - see the Sherman Jumbo as best example, it was not rare that units would bolt extra plates on the front of their Shermans as applique armor, or what ever else they could get as response to the very deadly German 7,5cm Pak 40 anti tank gun and just name it a Jumbo. But there have been also factory produced Sherman Jumbos designed as assault tanks to lead a column of Shermans.
