Rusev could also be a top level heel right now, but WWE decided it would be a good idea for him to lose to Cena on 3 straight PPVs, then be in a terrible love rhombus story, then join an faction whose only connection to each other was that they're not American.
Del Rio came back as a heel but was given the horrendous MexAmerica deal. Then joined the aforementioned LoN and lost his US title to a guy who is really just part of a tag team.
Bray Wyatt (I realize he is a part of the long list of injuries) could also have been a top of the card heel if he had actually ever won a feud.
I'm ok with Rollins as a heel for now cause he fills that role, but WWE dug their own hole of having no main event heels.