I've been having this exact same problem lately. When I first started playing the game, it wasn't an issue whatsoever. NPCs and players would load almost immediately upon coming into view. Now, however, they can take a good minute or two to finally manifest in front of me. The same goes for enemies sometimes too. I recently did a levequest where the "an enemy appears" message popped up, but I saw nothing until I was dead on the ground. Couldn't even target the mob by hitting tab. I essentially got murdered by an invisible force.

I don't think it's a graphics issue because I tried lowering the graphic settings, but it barely helped, if at all. I'm getting rather annoyed at this. Anyone that can possibly offer up some answers?