Odyssey is no longer AC. It ended with Syndicate Can have it's own title. If you take out the abstergo portion of the story, it still works. It doesn't need to be included in the first place.
FoA ep2 seems longer than previous dlcs. Or maybe the fallens have damn high hp or def, take too long to defeat than usual. Anyways this gen not many make decent quality and length dlcs. This is definitely one of them worth supporting.