A round number for a "completionist" playthrough, which I've done myself (and finished just very recently) would be 100 hours.
It can be done in perhaps 80 to 85 hours if you're "faster". I for one played on Hard, and finished it at Level 24 and a half or so, and my load saved game indicates 97 hours. I would probably have to remove maybe 4 or 5 hours from that count because there were times during which I let the game run (just paused) while I had to go out and forgot to close the game, happened a few times, so it didn't count for actual play time. So in my case I'd say all in all it probably was around 90 to maybe 92 hours.
Going beyond the 100 hours mark is probably because the player simply takes his/her time on purpose and just does everything very slowly while not only doing the actual tasks but merely stopping by to look at the environments, taking pictures of the scenery (which I did myself a few times), gathering materials for the heck of it (even without the need to, just to have something to do while exploring), etc. If I wanted to I could have stopped by some waterfalls and could have stood there for 2 hours, but I'm not that patient. Not to mention that some people role-play a lot (I do, but I'm more on the "casual" RP side of things in BioWare games), so I can easily imagine someone staying in Skyhold's tavern for 2 or 3 hours, or just walking around Redcliff for fun for another hour. That certainly "inflates" the game-play time without necessarily accomplishing anything (other than observing, and role-playing).
I would find it tough to believe that outside of doing the above, if a person only wants to "complete" things that can be done and call that a completionist run (like I and many others did) then that's about 80 to 90 hours I'd say, 100 tops. Beyond that - to repeat myself - is probably because the person takes their time for 'x' reasons and on purpose simply because that's how they like to play (which is completely fine by the way, everyone enjoys it how they want to). Honestly though, 200 hours... that would only be someone who just keeps playing the game after they beat it and the time accumulates on their saved game (there's no real reason to continue playing after you beat the game by the way, it's "there", you can explore, or re-explore if you want, but at that point the game becomes a void and feels lifeless, might as well just restart a new one).