I'm more worried about the quality than the length. I tend to take my time with these games, I've seen people finishing their first playthrough of Dark Souls III in 18 hours, so reports on how long Souls content is means nothing to me. What doesn't look too good, though, is that I didn't really like what they showed of the DLC. Didn't inspire confidence at all, and the first impressions we have now in the form of reviews aren't too exciting either.
At this point I'm just playing to see where the story goes. I've read some descriptions that got my interest.
Whether it's a good thing or not is up to the individual but that's how Miyazaki wanted it. I'm kinda disappointed about it too but not as upset as others are, what we got was well crafted so I can't complain, I'd rather take that then new but poorly thought out.
I wasn't bothered by it in the main game, but when Miyazaki started to talk about the first DLC and how it would allow us to look at DS3 from a different perspective, I was expecting some brand new stuff. Then they announce the DLC, and I'm thinking, "ok, Ariandel could be the original land that Ariamis used as inspiration to draw his painted world, I'm excited!"
But nope, it's another painted world. And all I can think is: "really?"