Has anyone ever figured this out? For all you guys who were in the beta, was there anyone who accumulated all the known items or at least all the useful ones? Based on the list of abilities set out in the wiki, there does seem to be
Not that I know of. I don't have the exact number but I believe there's over 200 legendary items alone. You will find legendaries if you play a lot, especially in the beginning as you complete the treasure adventures and quests, but eventually that slows down. I'd say after that initial rush I would be doing well to find 2-3 legendaries a week, with multiple hours of play most days, players who try to max out MP each day could do slightly better, but that takes a lot more time. Than on top of that there's a lot of epics to find. I do think it's very achievable to get all the rare cards you want, simply by replaying the adventures at a similar level. You get enough rare cards from those chests, that over time you'll get everything you want. It can take a while (it took me months of almost daily play), but you find a good amount of rare cards just for playing.
It's very comprehensive. Might be some stuff that's not in there, but I'd say most of it is. I bet Phase has a good answer here.
There are 1496 items currently active in-game. Find other statistics here. edit: There are other useful snapshots like the item vs token distribution and the cards unique to item data in the wiki. Feel free to browse.
Hmm... 1496 doesn't seem like much. It would seem to me that after 6 months, most regular players should have cycled through most of the items even without club membership. Is there any intention for expansions etc? I would assume so but I would hold off buying the basic set / club membership until the number of items significantly increase.
There were something like 2500 before they reduced items due to cards taken out of circulation and/or duplicates. A lot of cards exist in monster decks et c that could be slotted into gear in the future, even without any major expansion. I'd not worry to much about items - there will be more.