Quote Originally Posted by Packetdancer View Post
they've acknowledged it was a poor choice on their part to have the arena grow after the fight is underway, for precisely this reason.
Which is the wrong takeaway for the devs. The big issue is changing the arena back at the end of the fight. You spend a little over 80% of the fight with the arena in the triple platform layout, the enrage occurs with the platform in the triple platform layout, then you kill the boss and it reverts to the single platform for no reason. The solution is simple: don't revert the arena at the end. It's something they've done before too, just look at Diamond Weapon EX. You load into the fight, there's only one platform, second spawns, finish the fight, and the second platform remains. The arena change persisted after the fight was complete so people could easily place waymarks without third party tools. In fact, this is something they acknowledge they've done in the past. To quote The Lodestone post itself:

However, in consideration of duties where the battlefield changes during the battle, we allow players to place waymarks for the changed battlefield after completing the duty and save them to be used next time. Therefore, waymarks loaded from the save slots are not determined by whether or not they are in contact with the ground.
So yeah, that's all they need to do, keep the triple platform layout after the clear, and probably move the loot chests so they appear on the north bridge or something. Except they aren't actually gonna go with the simple solution for whatever reason, and instead "certain fields will be made slightly larger so that it will be possible to set the same waymark coordinates as in the currently widespread data, but through legitimate means." Clearly the smarter solution than just doing what they've done in the past with fights that have changed arena layouts. The whole situation is dumb, the arena changing back at the end should've been caught by the team that playtested the fight, and it sounds like they're making more work for themselves in the long run.