I think a big issue with the combined page is that the dismiss button becomes non-functional. I like to quickly glance at the new topic list, open any I care about in a new tab (often none), and then hit dismiss all. Now that this will also dismiss topics I’m tracking, it’s useless. I nearly dismissed this very topic just now by following this workflow.
It would help a lot if the tracked/watched topics were always on top. They are far more important than completely new topics, so I think this would alleviate much of the problems from combining the pages. Still sort them as they are today, just within these two sub-groups.