I pretty well have to agree with this, if only tangentially.
For starters, it's just weird expecting realism from a game, let alone this one. It's going to be ridiculous, or it's going to be a little more ridiculous. Not much of a difference at the point where something who's head has been cloven open several times is still attacking you.
150x same mob = mob's layer of depth (x % of unique behavior or abilities it's able to use) + mob's group strategy layer of depth. Not much of an increase, especially when, as is common for AOE situations, much of their 'uniqueness' will go unseen due to being killed too soon. Yes, group aspects of strategy come in and of their own, but they're nothing great. Each person does their job right, repetitively, and you'll hardly notice in your typical xp party. And in current implementation, there's virtually no unique mob 'group' behavior.
I don't necessarily see that as an argument for a specific length of fight. It's just that with the reaction speed of this game, using any weaponskills at all requires the mob to survive the first caster barrage, and won't be worthwhile without the target also surviving the rest of the AoEs. At less than 10 seconds a mob, granted that can be a bit of an extreme, we essentially are only using 1-2 abilities per class. Fire-Fira, Pummel-Aura or just Aura. Hence the lacking 'depth.'
If the game's reactivity were faster, time's requested would change again; it's a matter of steps, not seconds. If AoEs weren't the only thing viable for these situations, time changes would have already happened naturally. Doesn't matter how the added depth is accomplished.
Some random stuff that would add depth as long as the gameplay needed could be done:
- More AI behavior based off group combat, perhaps including triggers from nearby ally deaths.
- AoE maximums or fewer "pure AoEs" (damage dealt equally over area, and instead something like damage starting in the center and being absorbed or reduced from maximum as it expands outward, or the opposite; more unique patterns)
- Ways for AoEs to play off 'source' ST attacks
- Reasons for patterned orders of killing
P.S. Someone's probably already said this before, but mob difficulty doesn't have anything to necessarily do with leveling speed, as they can always award more xp proportionally.