To those of you that have the Quartz add on, you know that it shows you how much lag is being experienced by the current spell cast and is not affected by the "normal" latency meter. I'm just wondering if this is normal for most of you:

Traceroute to the edge of the WoW servers, for me, is usually 200-240ms (quite consistent).
In-game latency meter varies from 300-500ms depending on time of day, server load etc.

Quartz spell cast however, usually records lag from 350 all the way up to 800+. I'm just curious why a traceroute gives a latency of 220ms while casting can lag up to 800ms. It just seems a bit weird to me. Anyone have any ideas why this occurs?

Quartz updates the latency earlier than the WoW in-game latency. Just mouseover the in-game WoW latency every 2 sec and you'll see that it doesn't always update on time.

Plus, if your addons are communicating with others in a raid, there's a lot of information being sync between parties. Examples of usage is Omen, KTM, any Damage Meter, SCT, any Castbar addon. With so much data travelling to and fro, you may get lag in graphics updating (dunno how else to describe it). If you replace your addons with less syncing or turn off the syncing option, you'll see that your Quartz red bar becoming smaller.