What would the game be life if everythign was single target?

[Jojoya]

How would you think the game would be like in that scenario?

A series of Sastasha-style dungeons.

Where's the unsubscribe button?

No seriously, I get what you've done here and it's very clever.. With no AoEs in the game, it wouldn't be really practical or advantageous to mass pull, and dungeons would take a lot longer!

Except players are only willing to spend a certain amount of time in a dungeon before they decide it's not worth the trouble.

Make every dungeon take a long time and they'll stop running dungeons, which likely means they'd end up quitting the game if completing dungeons is required for progression.