I find I use my 15 ltd, 35 ltd and 55-300 equally for all sorts of landscapes. If I were missing any of these, I would find my creativity and compositional options severely limited.
The 15 is great for sweeping vistas, and its rendering (especially with the sun) is just amazing. The 35 is excellent for normal perspectives, giving a real sense of scale to objects (in addition to being easily the sharpest lens I own). The 55-300 is great for shooting targets miles away, and especially for being creative with perspective. And as a bonus, they're lightweight, so I can carry them hiking for miles without feeling strain. Sure, the 55-300 is not exactly the sharpest telephoto lens around, compared to say the DA* 60-250, but that lens is a monster that I wouldn't want to carry up mountains.
Anyone who says "UWA and be done with it" is limiting their creativity. You need a wide range of focal lengths to get the most out of landscapes.
DA 15 ltd:
DA 35 ltd:
DA 55-300: