Honestly, I like it exactly the way it is: A blurry trinity that allows you freedom to think outside the box of you "role".

It allows for freedom of gameplay. It diversifies the playerbase. It gives jobs low skill floors for more casual players but high skill ceilings for the more driven.

I really think "trinity" or "self-sufficient" is a false dichotomy. Why not both? Each is self-sufficient in solo play but in cooperative play each brings skills to the group that diversify them and they fulfill different functions organically. Oh wait, that's basically what we have.'

Everyone complains a lot about people who don't play how they like, but really how often does it happen in practice? I've never once encountered someone who tried to kick me because they didn't like my heals. Or back when I didn't know better and stacked full vit as a tank? Still no issues at all. It's working. It's fun 99% of the time. It's fine.