My solution not only quit rconomy problems, do bots no reliable, but also take a better multiplayer experience
1-BAN MULTIBOXERS, Ok, take them some days to dont do again, but dont allow more multiboxing.
2-Legendary 62 and 63 items only drop in parties with 4 players!!
1 player only, legendaries up to 60 level (can add rares up to 61 level)
2 player parties, legendaries up to 61 level (can add rares up to 62 level)
3 player parties, legendaries up to 62 level (no rares restrictions)
4 player parties, legendaries up to 63 level (no rares restrictions)
Why this? So players focuse on parties and bots become less reliable. No more hundreds of unid items. Your items have more value because bots cant farm them
Ok, this can take some problems to people that dont like parties, but better this than a dead game by bots and multiboxers.