See, this is exactly why I wondered about this... I know that Miura did art and Buronson did storyboard for at least two comics...
There have been rumors that Miura studied under Tetsuo Hara (Hokuto no Ken), but I don't know if there's any truth to it. I'm asking here to see if anyone knows if he was an influence on Miura at all, since I do admit the styles have some similarities.
As artist myself, I've noticed that Miura carries the style of early renaissance printmarkers. Though, I haven't actually read anything on this. If you look at works by Martin Schongauer and Albrecht Durer, you can see their influence on Miura's later work.
Another thing, Miura must have did a little bit of study about the renaissance, because most of the armor, swords, crossbows and etc were typical for the 14th and 16th century. AND also, the name Farnese comes from Pope Paul the 3rd, Alessandro Farnese. Who comission Michelangelo to rebuild his "Palazzo Farnese."
So this is all suppose to support my idea that Miura's influences are early renaissance art.