Darkhold, could it be better?

[Jennestia]

I could definitely be wrong but wasn't that originally implemented to limit the big summoner/mana burns because you can't chain the entire zone?
Now with EXP chains... I'm guessing it would be even worse if MOBs didn't return to their territory
Imagine killing 60 MOBs at 1 time... all at 150% bonus EXP

You'd just fight them in territory like most powerlevels does. (It's risky because of repops killing lower level people.) As for summoner/manaburn, no this wasn't in response to that because it continues in Abyssea with Fellcleve/Charged Whisker burns -- mobs have very, very short leashes in this game.