hehe nearly same op history i got.
started also watching one piece on RTL 2, but started a bit later with it, first time i watched it was arlong arc. Since then im hooked to it.
Normally watched rtl2 for pokemon and db then one day i started watching one piece, so it was my first anime of the...
I don't think Zoro had to fight with other creatures, can't see how this would improve his swordsmanship. And he sad that all that's left is mihawks head ( http://www.mangareader.net/103-56928-3/one-piece/chapter-597.html )
And Zoro already survived one hit from mihawk (...
I think it's because his slash is more like compressed air because of the force of his swing, with CoA u can imbue weapons with haki, but i can't expect u can imbue air.
My guess is that it has to be solid to use haki with it.
Thats also the reason why he could cut mr 1 when he hit him...