The Ring once ranked a "Co-Championship", in the 1960s Middleweight division. However, this time I think you are making a mistake. Especially because Vitali was "Champ" in 2004-2005, then Wlad has been dominating the division since 2006. You can't ignore that. Second...we don't know if Vitali will ever come back.
The Heavyweight division was been dominated by a "Klitschko" since 2004. Nearly five years so far, wow.