Easy mode is down to implementation
I won't lie, there are some things said about the Instinct skill that raises some concerns: such as the idea that it is being fuelled by take-downs. I am hoping that this instinct bar is a ratings system. That is to say that you start with a full instinct bar, and it only goes down when you go rambo, but otherwise remains full. This means that those who goes in guns blazing will lose their instinct bar (because they won't need it essentially), but those going stealth will not need to worry about it regardless of whether you kill 1 or 50 people during a mission.
But the instincts bar need not necessarily mean a bad thing; at the end of the day whether it becomes a fun game addition or just becomes a stupid easy mode game ruiner depends on a matter of implementation.
Because it is essentially a game at heart, there are some things that games just cannot replicate in real life. For instance if I was hiding in a room in real life, I can easily just listen to the footsteps of the patrolling guard outside the door to figure out his patrol pattern. And unless each gamer has a full surround sound system set up, and the volume turned up so high that will wake every person in the house, the dog out in the yard and the neighbour's cat 3 doors down, it can be difficult to expect in game footsteps to have any meaningful use. In this case, an instinct skill that let's me see an xray view of the footprints on the other side of the wall can be a more practical implementation that will make the game more fun. As the devs have said in the Q&A, it allows you to stay inside the game more, as opposed to menu tabbing out to a map to see where the guards are patrolling.
I just hope it doesn't end up doing something retarded like highlighting targets of interest, or highlighting "points of interest", like a giant arrow pointing to the closet you can hide in.