I got all of mine in Mooshu. I couldn't figure out where to go in Wizard City so I decided to head over to Mooshu for some boss battles and along the way, I found tons of Mist wood laying around on the side streets
The Bazaar has a Reagent Selection that will show what you want, altho' you might have to reload the selection several times, before the right item appears. And I have seen many vendors on the streets of Marleybone, so it stands to reason that there must be vendors all over the place. Maybe even the stores we are familiar with have stock of gems, minerals, etc.
I too had a hard time finding mist wood in Wizard City because everyone is looking for it there. When I did find it though it was on Cyclopes Lane. Hope that helps!! I'm going to follow the other persons idea and go to Mooshu to get the rest that I need!
Mistwood can be found in maby places. Just avoid other gathers and you should be fine. I have found it in the commons of GH as well as outside of that, in WC I have found more than a dozen places for it to spawn. I haven't seen it in Marley though, etc. Again, if everyone wants it, it will be gone fast...if you are on the east coast, try when you get up (6-7am Eastern is dead here) and westcoasters, try before bed, again, 1-2am is dead here.
If your sleeping hours are different, do as I did yesterday, take a nap, then come back during the dead time :-)
I find regents like crazy when I play, but that's probably because I'm on usually after most people go to bed. On average, I get two to three different regents in one try, I'm guessing because they've been sitting there so long. I've noticed that if you pick one up, that just appeared, it gives just one, but if it's been there a while, it collects multiples, and even more rare regents with it.
As for all the places I've found Mist Wood, well, every where in wizard city. Like some one else said, try to go some where no one else seems to be. Good luck.
The easiest way to get mist wood is to just by it from a nearby reagent vendor or at the wizard city bazaar. I remember i found some, I think in triton avenue but I'm not sure. But if you craft, it's just easy to just buy the reagents.