Originally Posted by
radioactive_lego
Yes. There doesn't seem to be a limit (or, at least, it's higher than 33 or 34) to how many mobs you can aggro. We scouted a few locations with dense populations of low level (less than level 20) mobs and tried to triangulate the best point inbetween the groups to get all of them on a single Pally spamming flash. 31 was the highest count we found (pardon me if I dont divulge the location) on a point where we could "hold" mobs. Additional mobs would come in flash range of that point, but the mobs would reset before they would physically attack the pally.
So to answer your question more completely: Flash, specifically, doesn't have the same upper limit that a damage spell does, OR it's hitting a different set of 16 mobs each time you cast.
My gut tells me the latter is true, and that dmg spells are hitting the 16 mobs that have the highest emnity to the caster, while flash is hitting mobs that have the lowest emnity to the pally. The only way to set this is to have a BLM/WHM sleep 16 mobs and mark them with various tags, thus receiving direct emnity. THEN have a a pally flash them (as well as having a group of mobs that the pally aggroed) and see which mobs die in the ensuing Holy/Flare. If the tagged mobs die, it's emnity related. If not, it's random or using some other unseen metric.
Because science.