Hmm. Lets see about Otto:
Diplomacy: 21
Martial: 5
Stewardship: 18
Intrigue: 16
Learning: 17
One thing that occassionally goes unmarked is Otto's silver tongue, or quill, as it may be. His ability in the show to play on Alicent's fears that her sons would necessarily be killed by Rhaenyra if they did not take the throne in order to convince her to join his plot was pretty astute, and his negotiation abilities may well have saved the Greens when he convinced the Triarchy to join the the Green wareffort. So just a hair above Viserys, but for very different reasons. Viserys is good at making himself well liked and respected by the people who encounter him, Otto is good at playing on peoples' fears and desires in order to compel them to act as he wants them to.
Martial, Otto has no noticeable achievements commanding troops, and his inability to muster a defense of kingslanding during Daemon's coup speaks poorly of his abilities in that regard.
Stewardship, Viserys seems to have handed over most of the duties of managing his continental empire to Otto, who seems to handle it rather astutely, if perhaps not all that exceptionally.
Intrigue, Otto is clearly pretty skilled in cloak and dagger efforts with his masterminding of the Green conspiracy during Viserys' life time, his arrangement of the marriage between Viserys and Alicent in the show and his dealings with Mysaria, but the events of Daemon's coup, which ended up with the death Otto's son, the captivity of Otto's daughter and Otto himself being beheaded mind, show that the likes of Daemon and Larys play on a far higher level than Otto in this field.
Learning, Otto is widely considered to be a learned man, and Davos is even told about Otto as an example of a learned hand who nevertheless wasn't a successful one, but Otto has no Barth scale accomplishments like authoring the doctrine of exceptionalism, authoring most of Westeros' legal code and authoring several books to warrant him being given a score in the twenties, unlike Barth, who was probably the most learned man to ever reign as hand.
Edit: Ironically looking at it Otto and Daemon ended up with a total stat score that's exactly the same, 77 points total, just with wildly different distributions.