I'd agree with you that the Trots will be lucky to pull in 3% between them. I'd also agree that Eva Joly is quite unlikely to do better than Mélenchon (though not for the reason you state - EELV will have a hard time because Joly is not an obvious candidate, and because the Verts have decided to throw the presidential in return for legislative seats).

But "We're all over the debacle of 2002", who dat? I think a lot of voters have firmly fixed in their minds that the first round is not to be pissed around with.

It's not my preferred set-up - the more Seriously Centrist™ Hollande is, the more I want to bash my head against the wall. But not so much because of crudely electoral designs. Much more because the time ahead calls for a political discourse that compellingly narrates... reality. Just watch the people flock to it if that happens. But Mélenchon isn't narrating either: just throwing lighted squibs.