Hellickson went #1 overall in my new dynasty's prospect draft (still no MLB draft 'til Thurs), and I haven't had any drafts yet, so I can't speak from experience.
I haven't heard anything about Hellickson not making the opening day rotation, but to be honest I haven't kept tabs on him lately. On ESPN, he's being drafted ~163rd, which I guess would be 13-14th round. That might be a little early for my tastes, but from what I've read that's about where he's going everywhere. If he can get anywhere close to 200 innings, it's probably worth it.
As for those pitchers you listed, here's where I have them:
The only reason I have Minor so low is because he's the only one I'd be concerned about IP. I like Chacin a lot this year, and if we're basing this on ADP, I love Gio. Out of these 6, I think he's probably the best bet to significantly outperform his ADP.