Yeah, that does sound weird. It must be something technical, I don't see how the positional updates would be lost or delayed with this good of a connection.
Your game sounds intresting, always nice when someone does something original. And I dont think you'll have to keep the updates very low for the main players if you keep it at 10. NPC's don't need constant updates or c_move(), they should be handled via pathfinding. All you should do is send an skill indicating that the NPC should move, then on each computer move it via pathfinding sperately. For my projectile weapons, I just send a skill to their instances saying "move", then they move on each computer according to their code seperately without any further multiplayer updates. Another thing, if your game is like diablo, then it won't be as fast paced like Unreal Tournament or something, so this should make multiplayer coding a bit easier in the long run. Of course I dont know the exact details of what your planning, but mabye you can get away with constantly updateing only some core entities.
And I dont think you'll have to keep the updates very low for the main players if you keep it at 10. NPC's don't need constant updates or c_move(), they should be handled via pathfinding. All you should do is send an skill indicating that the NPC should move, then on each computer move it via pathfinding sperately. For my projectile weapons, I just send a skill to their instances saying "move", then they move on each computer according to their code seperately without any further multiplayer updates. Another thing, if your game is like diablo, then it won't be as fast paced like Unreal Tournament or something, so this should make multiplayer coding a bit easier in the long run. Of course I dont know the exact details of what your planning, but mabye you can get away with constantly updateing only some core entities. 
