The second issue, we're going to need some images for. It's actually as big a part, if not bigger, of running around and around columns being good for dodging as NC's dodgy client-side clipping is. Imagine you are fighting somebody near a pillar, like in Pepper Park 1. As they run to the pillar to hide, we have a situation something like this:
http://cmaster.linxsoft.co.uk/images.../nc%20edu1.gif
The blue circle is you, the red the enemy, the pink is where YOU see the enemy as being.
In this situation, everything works out fine. Your client announces "I am firing at the Enemy with X% accuracy" the server does a check for line of sight and range and damages the enemy.
However, a second or two later, the situation has changed to something like this:
http://cmaster.linxsoft.co.uk/images.../nc%20edu2.gif
This time, the server notices that you don't have the line of sight, and your attacks do no damage. As the pair of you circle the pillar, this is how things are most of the time. You can't do much about it as the pursuer. Attempting to go ahead to where you would have genuine line of sight means that you lose the ability to target the player. Moving well ahead to ambush means you have to reacquire your lock again, by which time they are round a corner once again.
Now, something could be done about this with lag compensation, however you begin to see some of the dirty flaws in the system.