I doubt that many people, including die-hard Claremont fans, think that this omnibus is Claremont's greatest work. However, we know that there are enough Claremont/X-Men fans who will buy it regardless of quality (see last year's Marvel Universe by Chris Claremont OHC) so it makes commercial sense for Marvel to collect all of the Claremont material in one place - think of it as being like a 'bad bank' where the most toxic assets are held separately. And this way, the less toxic assets can be shifted into potential pre- and post-Revolution omnibuses.
Of course, it may be that I'm being a bit selfish here since I'd prefer that Dark Seduction and X-Men Forever are collected at the back of a potential Alan Davis Omnibus since that's the only omnibus I'd buy from this era...