Primary cause of T5 Divebomb failures

[synesthetic]

I don't even understand how the mechanic works, all I know is, stand here when you hear a sound run away, and repeat

It's because height elevation messes with AoEs. Most AoEs have a pretty limited vertical range. And as you can see for divebombs, it doesn't take much height difference to avoid getting hit.

Chimera's another example of how it's used; it's why everyone pulls Chimera to the tree on top of the hill, so that ranged people don't have to worry about Dragon's Voice, and then you only have to worry about silencing Ram's Voice to keep melees safe (although most players nowadays only know the hill part, and don't silence Ram's Voice).