Maybe it was a strech for you that Aria "got NTRed", but a few years and few hundred miles distance is just that strong, if you happen to meet that kind of... person. - I mean if you happen to love that kind of person who is basically a pushover from your PoV.
However I disagree with you saying that Wazu's only development was at the "final confrontation" with them, at the start of that arc I especially felt like "oh shit, we went back to where we started"... Clearly he was not that stagnant if there was somewhere where he went back from. Well, it was just my feelings ofc.