Basically you need to understand why Blizzard UVs look like that. They are very straight and aligned to a grid because the texture resolutions are very low and they wanted the pixels to be aligned with the seams. The seams of both of the hands are done very similar to the 2nd image you posted, the only difference between…
You can also use the ordinary transformations that you would use in the 3D viewport. So to align some verts along the U or V axis, just type 'sx0<Enter>' or 'sy0<Enter>'. Then you can continue to move the verts wherever you want them. You can also use proportional editing, sculpting tools, and all the rest of your ordinary…
There is no easy one-button trick to do this. You get that kind of UV's because the algorithm that unwraps the UV's aims to reduce stretching and pinching, meaning that it tries to create a uniform texel density across the entire model. This is usually not what you want when working with low poly and/or hand-painted…