Echoing the above comments. When they announced Witcher Senses it sounded like it wasn't just going to be like a Batman Vision that only tells you information you need to know, but would actually show general monster tracks that weren't related to anything. They never confirmed that, but it was just an assumption based on what was said.
Now chances are that was probably cut because a system that has to track literally every creature on-screen and keep a bank of its movements for the Senses would probably be way too stressful on the PC/Console. So from what we've heard in the previews, it sounds like the Senses is just your typical Batman-style vision where you're only shown what you need to know, and therefore there's no actual "proper" detective work on behalf of the player, when you find the glowing thing, that's it you're done, because it's always quest related.
It's a little disappointing, I was expecting a more robust system and I know that when I watched the 35 minute demo and saw the senses used, I just kind of hoped that it wasn't 100% complete, or that we were only seeing Johnny's tracks because no monsters had walked past yet. Ultimately though as previously mentioned if there's still some decent variety within quests, and the senses aren't just hammed in for every second quest, then it should be fine, but we'll have to wait and see.