Honestly from a lot of developer interviews I've been reading thats a universal. The more Marvel was balanced the worse it performed because it wasn't as exciting. Same with some early Melty Blood stuff. In general, what draws success more than anything is letting shit rock. You can't allow a game to become too broken, but you generally seem to do better when everyone has a few busted things than no one from what the numbers say. Folks like to feel awesome and in general powerful shit gives folks a thrill. Whether its Polimar/ Casshern unblockables, Akuma tatsu assist + Berzerker slash connecting, or just someone gettin to go ham with their favorite character folks just enjoy things that are good being allowed instead of nerfed to shit or aborted in the womb.
That's why I play Ken. Tatsu is so free.