Personally, I really believe the UFC protects Rousey, she's a moneymaker and a publicity dream and they're going to run with her for as long as they can, which undoubtedly means less-than top challengers.
IMO, that's why she got Zigano to begin with as her next opponent and then, Tate as her replacement, over say a superfight with Cyborg or the awesome Sara McMann(both of whom I believe beat Rousey). Also, take into mind that Zuffa didn't go out of their way to bring in Coenen, who would've been a stellar challenger, despite that Golden Glory heat. I appreciate that they have to build the division and Rousey is the far better ambassador for WMMA than Tranderlei Silva.
MY MMA RANKINGS
HW Cain JDS Werdum Cormier Barnett Bigfoot Browne Miocic Napao
LHW Jones Goose Evans Texeira Davis Hendo Shogun Manuwa
MW Weidman ASilva Belfort Jacare Machida Rockhold Munoz Kennedy Bisping
WW GSP Hendricks Condit Lawler Maia Kampmann Rory Ellenberger Askren Lombard
LW Pettis Bendo Alvarez Chandler Grant Gil Thomson Diaz J.Miller dos Anjos
FW Aldo Mendes Lamas Frankie Cub Lentz Kawajiri Zombie Elkins
BW Barao Cruz Faber Bibiano McDonald Moraes Assuncao Wineland Dillashaw