That's... dangerous.
The point about quests is that, basically, they DO transform any multiplayer RPG into a solo game.
Think about it. I have this quest, which requires me to kill 12 Winter Wolves. Ok, so I'm heading to the map with Winter Wolves. I kill 12 Winter Wolves. And then I leave, because I have no reason to kill more (you can make artificial reasons, like you need 12 Intact Winter Wolf Pelt, so I have to kill between 30 and 50 Winter Wolves on average, but it's still the same). And unless I have the quest to kill Winter Wolves, I have zero interest about the Winter Wolf area.
Now, I have a friend. But guess what? Unless we play exactly the same, at the same time, we won't be on the same quest step. I'm at the Winter Wolf killing, and he needs to harvest Alchemical Reagents, dodging Angry Treants all the way. So, I can go and help him, but I am not advancing my quest, and I am not gaining much XP and no gear, no faction, nothing. Or I can go kill my Winter Wolves, and my friend... well, my friend will do whatever he has to do at the moment. And we each play on our own.
With procedural generation, you might be able to do so. In which case, it's even worse. Because now, there is ZERO chance you both will be at the Winter Wolf quest step... because only one of you will ever have it.
This is one of the main drawback of the WoW model: you have those bite-sized content chunks, and you may or may not group up with people at the same chunk, but the next day, you won't ever meet them again. Even without the sharding mega-servers. Procedural generation amplifies this to the Nth degree, since, in WoW, you can theoretically keep on playing with 2-3 people for an hour going from step to step on the same quest. With procedural generated quests, after you've finished the Winter Wolf slaying, you have to travel to Winterdale to turn them to the tanner's trading post, while Joe has to bring the crafted result to Southshore, and Dave gets the potion in exchange, which is needed by the Lord of Ruin. Goodbye everyone, see you (or not).