And the reason there aren’t (m)any groups to join is because literally the only reason you’d ever run them on the PTR is to obtain crafting recipes. Once you’ve gotten those, you never need to run bounties again because you can get thousands of materials from the PTR vendor. Hence why I also suggested this months ago…
No, you are. Once you’ve gotten the crafting recipes you no longer need to run bounties on the PTR, regardless of whether that’s solo or in a group. Running a set of bounties gets you just 22 of each material. If you run a T16 rift in 2 minutes, that will earn you 600+ bloodshards. You then buy 12+ PTR caches which results in 1200+ of each material. So, 5 x T16 rifts, taking less time than a split bounty group, would get you 6000+ of each bounty material.