It’s a somewhat common misconception that enemies scale to your characters, but they don’t really. Enemies scale at a rate based on how many battles you’ve fought, what difficulty the battle node was, and what difficulty the game is currently set to.
Enemies scale at a slower rate if you refight battles you’ve beaten before.
Fighting “easy” nodes scales them slower than “normal” nodes, which is slower than “hard” nodes, etc.
They also scale slower if you have the game set to the easy difficulty, at a normal rate on the normal difficulty, and faster on the hard difficulty. The difficulty setting has no bearing on the current difficulty of the game; only how much the enemies scale for later.
So you can outscale the enemy the most by setting the difficulty to easy and refighting easy nodes. There are many mines/springs/caves/etc of any element that are repeatable, so you should be able to farm safely for any element you need. Some require you to rezone to respawn for some reason, though. For many nodes you can just stand in front of and fight over and over again, though.
Even if you don’t go through any of that trouble though, you get a lot of elements from the jobs and quests. So if your concern is primarily the elements, what I did was send as many people on jobs as I could and then refight a node until all jobs were done. Plenty of elements.
"It's not working. The banana is not melting."
-Masaokis