Okay, entire first wave of #1s are out now. And they appear to mostly take place in publication order:
New Mutants #1 uses the Moon->Starjammer gate from X-Men #1. The NM's absence (and use of the gate) is noted in X-Men #2
The Marauders group is formed in Marauders #1 and goes on to appear in X-Force #1. X-Force #1 is subsequently referenced in Fallen Angels #1 in a way that suggests it forms a clear dividing line in the early DOX books:
Spoiler:
After Xavier's death in X-Force #1, there's an official ban on leaving the island, which gives Kwannon some difficulty. Presumably, when Xavier comes back will be another dividing line.
Betsy arrives on Krakoa for the apparent first time in Excalibur #1. Kwannon/Psylocke III (there was another "Psylocke" in Cloak & Dagger? Seriously?) and her share an uncomfortable look (both are in civvies) and Betsy later reflects to Brian that she doesn't want to "spend the evening dodging the woman whose life [she] stole." Then in Fallen Angels #1, Betsy actually tries to talk to "Psylocke" and Kwannon brushes her off (Kwannon's in costume)
The big question for me is New Mutants & Marauders: Some plot points in the latter seem to be a lot simpler to me if Magik & Cypher are already gone...
Spoiler:
i.e., Magik can't teleport Kitty/Kate to Krakoa, and Cypher can't ask Krakoa what's up with her gate problem, if neither is around. Cypher's absence actually causes some trouble in X-Men #2, so that's definitely a thing.
Also, re: Fallen Angels #1:
Spoiler:
The issue retcons "Kwannon" into an alias, incidentally, one she's now rejected - I'm using "Kwannon" above for clarity. It also seems to suggest that this Kwannon is the equivalent of the Carol Danvers that was stuck in Rogue's head - or perhaps the Peter Parker "ghost" that was in Doc Ock/Superior Spider-Man's head - while Revanche was an entirely separate copy. like the Danvers that Xavier managed to restore from backup, or the Peter that died in Doc Ock's body.
Marauders #1 has to take place before at least New Mutants #1 as Logan's shopping list tells us there's no coffee on the island, but by the time of NM 1, there is. Add to that the general vibe of everyone getting used to Krakoa and this is probably very early in the sequence.
