I don’t think I remember a single mission that made you kill x number of y as anything other than a bonus, and even then, it was always a special number of elites that would be the only ones of that monster to spawn in that area.

^not always, some bosses summon additional minions as long as they live

Take out the minions first! You ALWAYS take out the minions first!

^  
That sounds… glorious.

If they made an MMO out of Ponies I would not want a mission like this.
 
More along the lings that I would want an antagonistic but open land with Changeling villages and a city with Chrysalis’s Castle.
 
The bad guys would be High Lvl Merc or Splinter Groups with Higher Caste sub Queens as bosses. Maybe one New Queen created to challenge Chrysalis who you have to stop before she takes over and starts a war.
 
The changeling lands being sort of a Cold War Zone filled with Wild Sub Sentient Changeling like creatures and population centers filled with changelings both distrusting and curious towards you.

Hrm. I’d prefer it in Guild Wars 2 style where anyone can join in and the event just gets ridiculous as 200 people fight off 1000 enemies.