What you tend to expect with NPB pitchers is that generally they pitch away from contact, and that they tend to use a lot of different pitches to get it done. There is a lot of deception involved, and the cat and mouse game between pitcher and hitter seems to be emphasized. Tanaka has several different pitches, as did Dice-K, as did Darvish. But you get here, you need to be successful in the strike zone, and the best way to get there is to go from throwing 6 or 7 pitches to the 3 or 4 pitches you command the best. Coming to the US, you'd expect Tanaka to be encouraged to stick with the fastball-splitter-slider combo and maybe tinker with another pitch. If his splitter is really plus-plus and his slider is solid, that is a guy with a pretty good chance for success.
Dice-K never simplified his approach as is necessary here. Darvish clearly has had no such issue - although you can argue that Darvish' pure stuff is better than Matsuzaka's. At the same time, Dice-K's consistent low BABIPs suggest excellent stuff which largely was ruined by crappy approach.