What do you want to see? Ngata finished this season with 63 tackles and 5.5 sacks. That is like less than 4 tackles a game and like .3 sacks a game. This isn't a glaring issue if you understand that in real life offensive linemen win the battle like 99% of the time.
To take it further Ngata's best statistical game this year had him make 11 combined tackles (8/3) and one sack. It is one or two games like this that get him into the Pro Bowl. What is really telling though is that in four games this season he had only 1 tackle all game and two of those games the tackles were assists.
Defensive linemen, especially in the 3-4 get handled all the time even by mediocre offensive linemen.
It's the bane of offensive linemen because they dominate all game and give up one sack or a key tackle and all of a sudden the guy who was getting his butt kicked all day long gets a Sportscenter highlight.
It is fine the way it is.