First Time With Citadel DLC-How To Determine Ambush Rescue?

Traynor has a small but amusing role in the main plot for the Citadel DLC (not sure how far you've gotten), so I suppose they had to keep her away from the main action somehow.

I agree with you that Citadel DLC feels a bit like an alternate universe - it's a funny and heartwarming coda, but not 100% consistent with the characters or the ME universe as we knew them. In particular, I suspect Bioware designed the very last scene with the assumption that many players would be playing it out of sequence rather than as part of a full playthrough. I almost always wait to play it until after finishing the story in ME3 - I load it up using the "legacy save" that the game creates and that starts from just before the assault on Cerberus HQ. Otherwise I would find myself wondering why these people who are so serious most of the time are yukking it up between missions so much.

Really disappointing that they didn't include the ME2 characters for the combat section of Citadel.

Can use them in the Armax Arena, so they'd work as combat squadmates. I guess they simply couldn't be bothered to record a couple hundred more lines of generic banter for each. Only for the ME1 characters because screw those ME2 schmucks.

Traynor could come too. Give her a gun and copy the powerset from one of the many ME3MP characters.

Instead you get canon waifu Liara if you were dumb enough to pick one of those wrong romances.

Jack's scenes are a nice addition to her story ark (if romanced)