On the 2016 primary debate issue, there's really nobody forcing the candidates to agree to the DNC sanctioned debates in the first place. In 1999, Bush was way ahead in the polls, and refused to participate in any debates until December, just a month and a half before Iowa. If the DNC had scheduled 20 debates and started them in April or May of 2015, Clinton would have just skipped them anyway.
And there was nothing stopping Clinton, Sanders, and all the other candidates from ditching the DNC debates altogether and just agreeing to a debate schedule of their own making. Except that, again, Clinton wouldn't have gone along with many more (and earlier debates), and no one would have watched debates without the frontrunner. So she was always going to have a good deal of leverage on this issue, regardless of what the DNC decided.
I would make an exception for the simple fact that you need to recruit candidates in tough seats in the first place to allow for circumstances to provide such a wave but both Perez and Ellison campaigned on doing exactly that, so...
How much of a role does the DNC even play in such recruitment? Isn't that more of a task for the DCCC and DSCC?