Story-wise, Ifrit, Garuda and Titan (Hard) felt absolutely pointless outside of an earlier comment about the need to re-evaluate previous encounters, but after unlocking and clearing said Trial(s), there's no follow-up at all to make it feel "relevant" for the - at that point - ongoing plot point. If they want to keep it, they could push the quests to unlock the hard version when it's actually required and add some short "I received the data from X after your rebattle with Y" to the Scion who gives you the quest for the next Hard version. Or let the game recognize you have already done the trials with the current version, instead of needing to to do them a second time (outside of intrinsical motivation or roulette purpose).

As for Quarn: It would have helped if the system had acknowledged retrospectively that you already cleared the dungeon; so that the NPC in front of the entrance could simply hand you the item over for some reason.