Now imagine a quest (or dungeon or whatever) where you play the role of a raid boss. It’d be like a bombing quest, but with strategy. Instead of hurling missiles at unsuspecting groups of NPCs, you’d be using a set of abilities to fight NPCs with AI that directly counters those abilities.
Imagine a 40 man raid with only one player. If players being fought by NPCs is possible (as opposed to NPCs being fought by players) it is also possible to fill empty spaces in a raiding team with NPCs made specifically for that raid.
If you think about it, there aren’t really that many pieces to even the most complex raid strategy: Ragnaros boils down to “don’t stand in these places” and Madness of Deathwing is basically “attack this thing before that other thing.”