World Bosses are inconsequential and time gated. It already needs to be fixed.
- Roll with 4 Affixes
- 4th Affix is never a GA
- 4th Affix is a Temper and can be Enchanted
- 5th Affix is applied via Tempering
- No Tempering Durability, cost just increases to a cap like Enchanting
- Once you get a GAIII item with the Affixes you need, that should be it. Considering the Rarity in a Season, this is more than fair.