To meet all of the criteria you listed, sadly, Canneroc was the best I found (once you get and upgrade your house). Most of the other stashes require too much running from the fast travel point to make them useful.
However, what I found while playing is that there were some locations that were good to go to if you wanted a smaller subset of actions (i.e., if you didn't need to hit your stash).
Of the maps I'm showing, the fast-travel spawn point is circled in green. Stashes (if any) are in red and the crafting stations and shopkeepers are in orange. The "load screen" count includes warping in to the town in the first place.
Canneroc (best for stash + all crafting)
Load Screens To Hit Everything: 5
In my opinion, Canneroc is the best place to go if you need to hit
your stash. The spawn point is right in front of your house, which
also contains sagecrafting + alchemy. Unfortunately you have to run
across the street to do blacksmithing and selling. You end up up
seeing 5 loading screens by the time you warp there and run in and out
of everything. Still the winner if you need your stash, though. Not
only does it take longer to get to your house in Adessa and Rathir
(waaaaay longer in Rathir), but once you get inside your house, you've
got quite a run to get to the stash in either case, versus it being
right inside the front door in Canneroc.
Didenhil (best for all crafting + sales, but no stash)
Load Screens To Hit Everything: 3
Didenhil is a pretty solid choice if you don't need to hit your stash
but you want all the crafting types. You've got Alchemy,
Blacksmithing, Sagecrafting, and shopkeepers all inside the same room
not far from the warp-in point. You'll only have to see 3 loading
screens by the time you warp there, run in, and run out.
Mel Senshir (best load time if you don't need stash or Alchemy)
Load Screens To Hit Everything: 1
Once I got to Mel Senshir, this is what I ended up using most of the
time, with an occasional trip to Canneroc just to drop items in my
stash. The main thing this one has going for it is that the warp-in
point is right next to two shopkeepers, and while the crafting
stations are a short run away, they are in the same zone as the
warp-in point, meaning you don't have to see any loading screens to
get to them. If load times are a pain for you, this will probably be
the one to go to. Since I found Alchemy to be a waste of time in the
game, this was my preferred salvaging/selling/crafting point.
I can't say that there's absolutely nothing better out there, but through the 40+ hours I played, these were the ones that seemed the least painful to me. Basically, I ignored Alchemy as a waste of time, used Canneroc to hit my stash, and use Mel Senshir for everything else. Before I had access to Mel Senshir I used Didenhil instead.