It was was 30-60 minutes long then it would likely be fine... It's just if you sink 2-3 hours or more into it, the pacing feels very weird for what's just supposed to be a transition event to get between the events the XNG lab and Omega lab. I think part of the problem is that being added after the fact, it feels like just a time filler for going between those two locations.
But, if you actually look at the entire story, the Omega lab was never your destination per se. The entire reason you went to Hengsha was to track the implant tracking device, and getting on that ship was just a lead... you had no idea where it was going or if
was there. So, if the fact it was a bit of a crap shoot was made a little more clear, and maybe the Missing Link involved a little more investigation into where
was, then maybe it would feel more natural. You knew the ships were traficking people from the XNG port reports, you knew one of them likely led to
because of
, but you really didn't know which... or how getting into a container would somehow get you to the right one without being discovered (since all the containers were in fact being processed, a sort of plot hole that Missing Link fixes by showing how obvious it was that you were discovered, and the only reason you weren't discovered upon arriving at the Omega lab is because of the new help that you received).
So, if the pre-DLC and DLC built that up a little more, it would fit with the story better. In terms of story and continuity, it makes a lot of sense -- it's just the reason it makes sense is sort of hindsight based on reflecting about all the emails you read. When you actually play the DLC part of the Director's Cut, knowing ahead of time you're going to end up at the Omega lab, it does feel a bit annoying to have this extra step because the story doesn't really build up our logical the step feels -- it feels more like an accident added just for the sake of extra content. But, in terms of story and contuinity, it does make sense. Had it been in from the beginning, they could have likely built up the anticipation of it, and the likelihood that you wouldn't just luck out and arrive in at the Omega Ranch lab, and that you would require an extra step (the DLC) to figure out exactly where to go next.
This is all excluding the actual gameplay pacing. It has a rather lot of backtracking for a Deus Ex game, usually something it's rather good at avoiding -- lots of options but always a sense of going forward. It's designed and paced out a bit like filler content, and could probably be 50% shorter or even more, and still achieve the desired story effect. It's still fun gameplay but it feels overly long compared to Tai Yong Medical, FEMA, or even Omega Ranch.