It definitely looks like Heathcliff's gonna distort, and I think we'll probably go through his story dungeon without being able to use him (Miracle in district 20 introduced fights where we can't use certain sinners, so it'd make sense to reuse that mechanic for canto 6) and eventually beat some sense back into him like he told us in the beginning.
In the original Wuthering Heights, Nelly recounts the story of Heathcliff and Catherine, so I think Nelly's gonna tell us Heathcliff's backstory rather than Heathcliff himself.