I think role quests in general worked in ShB because they sorta tied into the story, and at least they were providing some backstory for a character that mattered (Arbert) in addition to giving some info on the setting.

But, they kept them going for the same reason they keep most things: they're following a design document first and inventing story to keep it cohesive. All the tribes had a totem of identical make stolen by the same crew so that they could easily have all the roles conveniently in the same spot. This sort of thing is convenient to the player and developers but I think it probably limits what they can do with the story.

I actually liked the Tank one quite a bit, mostly because of the tribe introduced and the two Eyes' relationship, and the melee one because the stakes and my involvement didn't feel undercut by comic relief.

I don't know that this had anything to do with the piteous villain seeking revenge for their falling asleep on the job in the past or the tank role in particular.

So, these quests persist because at one point we had job quests, then we had a change of pace in ShB, and we're holding that pace because that's less effort for the devs to make a new or different system.

Why not just have these stories exist in the zones of the expansion waiting for players to find them? Did we need to have them tied to roles so we can unlock dye options for gear we use for like a day at most? If they feel they can't tell the job stories forever, fine, I get that, but why replace it with another system that has constraints on it that end up making it feel forced?