Just reposting what was said in Lani's project comments, and adding firther discussion.
I still think rep is much better as a drop rate source, ie the stamps / hay we currently have. That said, as much as I liked the hay for those reasons. I don't think it's best as a long term solution. As Lani mentioned in the project, Stamps are also balanced as it's a drop farm, with no need for an alt army, and agree with her that these are also a great avenue for a repeatable rep farm.
I will re-iterate stamps should remain as an un-tradable source to ensure balance, no skipping, and maintain appropriate lore (ie keeping it as quest rewards, or soul-bound item drops).
My first suggestion would be to add stamps to all fb/bh dungeons:
fb19 - Lv.1 Darkness Stamp (4 rep) - 2% (currently in game)
fb29 - Lv.2 Darkness Stamp (5 rep) - 5% (currently in game)
fb39 - Lv.3 Darkness Stamp (6 rep) - 5% (currently in game)
fb49 - Lv.4 Darkness Stamp (7 rep) - 12% (currently in game)
fb59 - Lv.5 Darkness Stamp (8 rep) - 17% (currently in game)
fb69 - Lv.6 Darkness Stamp (9 rep) - add to all mobs 17%
fb79 - Lv.7 Darkness Stamp (10 rep) - add to all mobs 18%
fb89s - Lv.8 Darkness Stamp (11 rep) - add to all mobs 20%
fb99s - Lv.9 Darkness Stamp (12 rep) - add to all mobs 20%
This will improve bh help, as well as encourage fbs/bhs to be done without wine - for the full challange. People who like to solo, can still farm rep from lower level fbs and are not dependant on help, but generally the same effort is required to farm rep on your character regardless of alts-army abuse, or team member dependant. In addition, being such varied locations, players can mix it up to avoid getting bored.
If we had something like the above in place, I would also suggest removing wedding candy trade from hay + wine and removing them as a reward from wedding packs (doesnt make sense - but has been a good temporay solution).
Also (and this may be controversial) - I don't think rep should be craftable from mats, at the mat trader. One-man already has a rep reward, so perhaps that could be increased instead, as it makes more sense to gain renown from killing things then from trading materials.
As I have suggested the removal of 2 sources, then increasing the rep reward from stamps (ie doubling them so a Lv.9 gives 24 rep) or increasing the drop rate overall, would be recommended. However I would be cautious to make such a big leap, and recommend first the above (adding to all fbs), and then if it's seen it is needed, increase the drop rates later. That way there is no anxiety over the future, and no thoughts to save up the stamps "incase they double" and avoid drama/distrust.
So to summarise:
1. Add Darkness stamps to all fb dungeons (69+) listed above.
2. Remove candies and mat trade for rep.
3. Increase drop rates of all stamps, if required.
After a regular farm is established and finalised, then other one-time methods for rep can be looked at as additional options (eg quests ect).