How will aggro be on mobs?

[Elexia]

Maybe I was just imagining it, but I thought enemies would aggro from a larger distance depending on how far below their level you were.

You imagined it. SE stripped out all detail like that when people were complaining that monsters were aggressive or would follow you and so on so forth.

What you witnessed was the server calculating you closer to the mob than you actually were, which is why you can't go from full burst running to walking next to walking mobs and not catch aggro, much like in XI you can drop invisible in front of a yagudo and quickly use Spectral Jig/Powder without catching wrath simply because the client has the priority.