Diablo 2 was also more direct trading. People had no problems waiting out for any commissions out there. I'm surprised that game is still alive as well as Albion. Diablo 2 gear is anything but lackluster. From what I've seen what keeps an online game alive is the community.
I also feel like direct trading fits more into the traveler/adventurer feel of Embers Adrift.
MMO vs small (like 4 person) hosted locally servers.
I don't think you can compare to the two games (Diablo 2 and Embers)
Direct trading was really bad in that game, it was full of scams and just not good.
If you are forced to direct trade only, it will be a very sad economy. People are not going to want to spam chat and read that spam etc etc. It's really going to just kill the economy. If this is the plan, you might as well say there is no economy in the game.