OK. I feel that this will come up sooner or later. So I figured I'd start the discussion. 1) I know many people don't care about timeline continuity in IA and I'm totally cool with that perspective; 2) I think FFG has moved away from timeline restrictions so I don't think that any of this will be limited by rules. But here are a few notes based on new Canon (not Legends):
MANY SPOILERS FOR REBLES TV SHOW, MOVIES, COMICS/NOVELS MAY FOLLOW!
1) Maul shows up at the end of Rebels season 2 (though of course he around before this) and dies in season 3. So presumably, HotE takes place somewhere around this time. It could be earlier but since Ashoka is going to interact with him in HotE, and she doesn't seem to know he's alive before Rebels season 2, I'm guessing we're pretty solid in the Rebels Season 2.5 - 3 window.
2) At this time, many of the OT rebel characters are not really in play. So Lando, Han and Chewie are living the smuggler/gambler lives, and Luke and Leia are teens.
3) OB1 is around at this point and living the hermit life beyond the dune sea, but based on the comics and Rebels he's not completely out of action. Plus, the OB1 ally pack is a good representation of his age at this time.
3) Technically, BT1 and 0-0-0 have origin stories in the Darth Vader comic that takes place between A New Hope and Empire. So they aren't technically around at this time (presumably their chips are in some ancient ruin).
4) I don't think we've seen AT-STs in the Rebels era but we have seen AT-ACTs and AT-ATs in Rogue One which takes place very soon after this, so presumably they could be around and in early development.
5) Rogue One will probably take place at the end of, or shortly after, the unreleased Rebels season 4. But I think it's fair to say that most of the Rogue One characters would fit into this timeline. Of course, Jyn Erso might be in prison or living under a pseudonym.
5) Most of the Imps are unaffected since we have Vader, the Emperor and normal-looking stromtroopers in this era. The one issue is the Grand Inquisitor who presumably dies at the end of Rebels season 1.
6) I don't know where all the Mercs are during this period. I think we get introduced to many of them in the later seasons of Clone Wars, so I think it's fair to say that most of them are around and kicking. Of course Greedo is ALIVE!!!
Thoughts on this?