how long does it take mobs to respawn, and when they do, how come all of them dont?  

It takes 15 minutes for map monsters to spawn.
But why everyone don't spawn every time is a good question

Sometimes they die globally, and take an hour to respawn.

does that mean that even if i don't personally kill them, if they die globally then they won't be on my map?

also, why does the world "lose focus?"

Yes. They have a health rating, and after a handful of strikes from multiple players, they die globally for a little while.

The world loses focus so the WASD keys work on the chat box.

ahh, thanks for the explanation on the global deaths  

i personally don't care for the world losing focus... but i guess that's just me..