Very little time core dev time from my team has been spent on curation rewards changes (maybe two weeks) or the apr savings change (this latter was 2-3 days probably). No core dev time has been spent on staking (yet), unless you count the past couple of days when I've had to follow the discussions about it to stay informed about proposed ideas.

There has been a lot of time spent on things like development process improvement (setup of continuous integration system and testing frameworks), code refactoring (mostly in hivemind, but some in hived as well), many bug fixes, optimization work for scaling, and developing modular hivemind technology to ease development of scalable Hive apps. These are actually really important things for future efforts, but it's easy to miss them because they aren't as glamorous or relatable as protocol changes.