The way people use it is you constantly reorder windows according to your workflow so DnD is not a problem.
> I'm also someone whose open browser tabs tend to grow indefinitely until I just have to bookmark and close all hundred of them or whatever
I agree the tab model is an horror. The problem is for most people the tabs are their browsing history, with a visual clutter.
My guess is there is an huge opportunity for rethinking the whole web browser history/tab model.