I can sort of understand the Witcher Sense ability, though I prefer how it worked in Witcher 2. Your medallion would rumble when you were near something magic, and it was up to you to find it yourself. For example, not many people would immediately know that there was a Witch in Lobinden outside Flotsam unless they paid attention to their medallion.
I'm also happy to hear that the segmented open world is being kept rather than a fully open world. It means that they're still keeping the open world localized, which allows for a much more realistic scale. (Flotsam, again, was a small fishing town and it was bigger than any city in Skyrim.)