Katasaki: I respectfully disagree about the Shimazu in campaign- you can take out the Imagawa in one or two years, and then you have only two provinces to garrison. Tech up a bit, then sweep into the Ronin-held Shikoku, and you're close to Hojo/Uesugi income, especially if you improve the farmland in Hizen, Chikugo, and Chikuzen.

Back on topic! Yari are useful, but I usually replace them with ND as soon as I can, and rely on YA to do the anti-cav work. If I can take height, the cost-effectiveness of the YA is impressive.