focus on dan, ned and any business tied to Steem and only upvote their post
That is actually correct curation given the current userbase.
It might even be correct curation later because, well, what else do all steem users have in common besides steem? The diference is that later ned, dan, etc. will likely make much less frequent steem-related posts, or their posts will be technical and nature and not appeal to all steem users, so probably only voting for their posts won't work. For now all their posts are of interest to nearly all system users, so it shouldn't be a surprise (or viewed as a failure) that they attract the most votes.