So, for those not aware, you have to collect 'Lost Treasure' by killing enemies throughout the system. When looking at the bounty on D2checklist, it shows that you need 350 of these lost treasures (the bounty itself in game just shows a %). So far, not a great problem. Get 350 kills and all done... Well, that's where the problem comes in. The actual drop from killing enemies is RNG as to whether you get a lost treasure per kill. From a very quick calculation after visiting the thrall pit in the Whisper mission, and checking the progress on a masterworked weapon, I estimate I was averaging 1 treasure every 10 kills. That leaves it as approx. 3,500 kills just to complete one bounty, which seems quite excessive (especially during an IB week when people will want to be spending time in the crucible, not killing thousands of PvE enemies).
That about what it took me about 3500-4000 kills I just grinded the thrall pit as well took me about 1.5 hours