Concerning "The Box", episode 17 of season four of "Star Wars: The Clone Wars": Obi-Wan Kenobi (working undercover, posing as the assassin Rako Hardeen) reached Count Dooku's palace on Serenno, and was treated as normal bounty hunter. Count Dooku was even happy with him because he was the smartest one among all bounty hunters. Maybe those hyper skills wouldn't create suspicion, but why didn't Dooku find him suspicious due to a disturbance in the Force?
I imagine that Kenobi used a technique known as force stealth to hide his presence from Dooku, just like how Dooku and Palpatine hid their dark-side presence from the Jedi.
From Wookieepedia's entry on Force stealth:
Force stealth also referred to as Force Concealment or Buried Presence was a power that was used by highly skilled Force-sensitives to mask their Force alignment (Light or Dark), their ability to use the Force, or even their entire presence from other Force sensitives.
Palpatine was the most powerful and notorious user of this power, having hid his dark nature for over three decades from the Jedi Council, even when in the same room.
Jedi Masters Obi-Wan Kenobi and Yoda both used a form of Force concealment to shield themselves from Palpatine and Vader in their exile.
This isn't a fool proof way to hide force presence, as in the episode, even Anakin at first didn't sense Kenobi as the disguised bounty hunter when fighting face-to-tace. But he eventually did, which I would attribute to his close relationship to Kenobi.
Kenobi doesn't have a close relationship to Dooku, so it shouldn't be expected for Dooku to immediately recognize Kenobi's force presence, even when in the same room.
For a canon reference, Kenobi was able to spy on Dooku in Episode II on Geonosis, when Kenobi followed Jango Fett there. Kenobi was in the same room as Dooku, and Dooku didn't sense his presence.
Since Vader could feel the disturbance in the Force from Obi-Wan from across the Death Star, and in the episode 17 Dooku was standing less than 10-20 feet from Kenobi when they met, I can only think that it was a plot hole. The episode is only 1 week old, so there are no retcons yet.
Well, it is obvious that Force Users ability to use the force was in decline, given the abilities shown in other places, it is obvious that during this time the Force was fading away, given the Jedi's inability to sense even the slightest deception or trap (but maybe that was just arrogance) and the Sith have the same issue. But since we've seen in the recent movies, The Force Awakens and The Last Jedi, the Force has seen an emergence in strength so that even novice force users are able to overpower and stand against trained and powerful practitioners... for all their flaws the new movies has started to make the Force as awesome as we all believed when we were children.