TLDR: Not enough quest mobs or quest items and to long respawns to house so many players. (not enough layers?)
There are so many players present in world that getting your quest item or quest mob can be really hard as you compete with others. Partying can sometimes solve this problem but it’s but a tiny bandage that will not work that great most of the time.
Even outside the peak player time there are some areas you still would want to avoid like Hilsbrad farms is good example. Where many single named mobs have to be defeated and there is waiting line of several parties.
During peak it becomes really ridiculous, you just watching grass grow in hope that maybe next spawn you’ll might be able to tag, it is but a chance tho. Layer swap will not help, you just enter the exact same scenario on another layer.
Trying out mage AoE farm can be fun, if you can look pass the fact the there are many other players trying it out and just about every second mage that run into you will try to mess you up or even kill you in attempt to avoid sharing the farm spot. And I get it, ppl are frustrated that they cannot play the game, it bothers me to.
But this is impossible for players to deal with, it has to be Blizzard making changes to the game that make it account for just how many ppl play the game atm. Some sort of dynamic spawn even for Named mobs. Or maybe more layers.
It wouldn’t be to much surprise at this point if people just quit the game for sole reason, well that they can’t play the game. Likely not something you want to happen over a situation that has possible solutions.