If those items would be delivered from a achievement, they would not be available on the loot chests.25 adventures is a very small number for an item that you cannot get from market. Rather those items should start after 150 or 200 adventures.
The only way to get those items would be playing on the adventures.
So if people wanted to get all the bandit set, they would need to take part on, at least, 250 battles. (nearly 3 days of intensive play online)
The AFK could be made on the registry by wins... but lost should be counted too.
Or separate the items in 2 categories: played and wins. Just used that to give an example based on the actual achievements that are active.