If your assessment is Marauders and Excalibur is dead on arrival,You are bad at assessing things imo. Marauders will likely be the 2nd or 3rd best selling X-book, Excalibur will probably numbers maintain just above cancellation range. People are mistaking not great "X-men" numbers aka bunch of books in the top 25 for not good numbers for any other comic book. While the X-men has not been monster it has been in the past using April comichron numbers for example X related books had 10 books with more 20,000 copies ordered and below 20,000 is normal point when books get canceled. Then they had another 10 books with above 15,000 copies ordered but below 20,000.
I don't support that theory I have seen X-fans pick up worse books than what is being presented in Dawn of X and that was without Marvel herding them all to buy 6 books with no easy option to avoid.In a world where Marvel was counter program itself with Wolverine and X23 solos and misc Iceman,Domino,Major X,etc books maybe. But We have seen worse stuff in X-men Gold, Blue, Red and Astonishing with Wolverine and X23 solos all stay above cancelation numbers. The numbers don't support these book will coming crashing down with only 6 of them around. Fallen angels looks shaky but other than all other books look solid. X-men should land in top 25 books monthly, Marauders or X-Force will get around 50,000 then degrade down, New Mutants with Hickman should do good let's say around 40,000 degrade down, Excalibur is shakiest of the solid bunch but I would bet on staying above the cancellation mark.