The final part of ARR story doesn't make enough sense.

[Aylon]

I believe merely for gameplay purposes. Story-wise, we do face each primal, solo.

I disagree. Story-wise we are always told to gather adventurers or get help. If it would be for Gameplay purposes only, why should the npcs mention it? Why would they show other Party-Members in Cutscenes in Dungeons and Raids? We really aren´t that strong. Story-wise I would consider the GC-Leaders, the Scions like Thancred, Papalymo, Y´shtola and Yda, the Ascians and the Garlean Generals stronger than us. Don´t think, we would stand a chance in a one on one. Even against the Garlearean Generals it was a 8 on 1 in most cases. We defeated Ultima and Lahabrea only with massive help from Hydaelyn.

Even in the instanced Fights in some Story or Class-Quests we wouldn´t accomplish much, if we wouldn´t have help from various NPCs.