Your Kursk example is correct. An analogy would be an unbalanced infantry regiment, with too many snipers and not enough general combat platoons. It would work fine in some situations, but your enemy would figure out your vulnerabilities and take advantage of them.
RE Kursk:
I seem to recall reading (don’t remember the source, but will research it) that Russian infantry units SWARMED over the Nashorn and Elefant crews and basically destroyed them before they could make any difference in the fight. Open-topped vehicles, no crew protection from air, artillery, morters, etc...