Aether Weighting: All Aether loads are weighted differently from engine to engine, and it appears that the NML engine is rather hard to fill, and you can draw the conclusion that Aether is weighted as less than the other engines.
Aether Entropy: As I'm sure you've noticed, the engine eventually slows, and the fog returns (GOing slowly back through fog levels). This is from Aether being used up as fuel. Thus, to keep the engine running, regular shipments of Aether must be added every 5-10 minutes. Again, this differs engine to engine.
Engine Update: Since the update and the tougher mobs, it appears that the engine has gotten harder to fill. We can only assume that this is because of the update and that the devs want more teamwork (As more and more things need at least one wing-man).
Closing Bias: I think if the devs want to add more teamwork, they should add at least 1 more spot to battles, maybe 2, on each side. This way, you can have all professions (and if you add 2, a slight tilt to that profession's talent) in a battle.