Tekken is the least volatile of all fighting games, Powerful characters usually remain powerful or near the top in power. Characters like devil jin, Steve, Nina, Jin Kazama, paul, Law, Julia as of late, all stay top or Near the top of the tier lists.
Street fighter on the other hand can have a different top tier every month, especially with new games.
Take sf6 for example, Kimberly used to be the best character in the game but one nerf made her B tier, Chun li was consistently a top level threat until Mai just did her job better. There is volatility which means top 8's and tournament winners change constantly. Just last year MenaRD won with blanka, Year before that it was Punk with a different set of characters, before that it was angrybird with Ken, yes those 3 have remained dominant, but they were all forced onto different characters in order to do so. Just look at the rest of top 8, there is no consistent set of characters or PLAYERS for that matter making top 8 compared to a game like sf4 or sf3.