Even if a level 50 Limited Job had about the strength of a level 60 traditional job, I don't think 『バチ』will have quite hit the mark. (Bachi -> Patch (pachi)? Bee (hachi)? I usually only see this term in CS, for batch filing, and doubt that's what it refers to here.)
If a level 50 party of 8 BLUs haven't at least the prospects in a given encounter that an undermanned party would have had in Heavensward, it will all be utterly without interest as content and I have no doubt it will be unable to sustain itself.
Using skills like Provoke (via enmity spells or by simply allowing us access to Provoke itself via Role Actions) and Mighty Guard and really letting us take up the tank role or the like, I'd ideally like for a group of 8 BLUs to be able to tackle Extreme primals. (It is technically possible already if your members are individually skilled and your party coordination crafty enough, but I would like for this to be much more regularly possible.)
If we get to the point where we can run as a group of 8 BLUs, I imagine we can make it far easier [e.g. less disrupted by job swapping and rotating who gets to benefit from others' sacrificed time on 70s?] for players to successively learn their spells.