Paladin Lag issue

Is it known whether the Paladin lag is caused by network congestion or cpu usage?
Maybe if someone is experiencing lag due to a paladin, check out the server stats page:
http://www.disastrousconsequences.com/mrtg/

To my untrained eye, those stats don't look too bad. CPU just ticking along. Network is probably the most worrying, but a typical 1.1Mbps max 4Mbps ought to be within the capacity of the server?
What am I missing?

Actually, is UT2004 single threaded? In which case the cpu is a bit heavier than ticking along, but still not maxed.

I believe UT2004 is single threaded. It only uses one core on my system. Also the P4-HT was released in 2004, so it is likely there was no reason to make a multi-threaded game.

What was the scenario when the cpu was heavier? Was this on your own setup or on DC?
If on DC, the stats page interpolates the cpu load over the update interval. If it only updates every 5 mins, the load could be at max at some point in the interval.

I had an issue on my old server where some of the monsters spawned were too big for the area they were spawned in. My cpu load was maxed out (causing lots of lag) until that monster was killed. I didn't really experiment much on it, just reduced the monster sizes. (I don't remember if it was all monsters, but I do remember the red gnats also suffered from this if they are allowed to get too big)

Would it be possible to shrink down the size of the paladin and see if that reduces the lag? It also will help make room for other players, and reduce the number of paladins getting stuck in doorways.