Update/dualboxingblogs:

So I noticed the lag goes completely away when you're in an instance. Which is great, because that's my main method of leveling. The instance quests give huge EXP. When I hit the assist key it immediately grabs on the followers, but when in the open world it's much more laggy, but bearable.

Regarding cast sequences, you pretty much have no choice but to use the ISboxer stepping. I tried to fumble around with macros, but it definitely was gimping all my dps. It was pretty easy to figure out actually. I'm pretty sure I'll even use an "on release" eventually as my group levels higher, but for right now sending 123 is working fine with my macros.

Warlocks seem incredibly weak at low levels, my hunter and monk easily do 4 times as much damage. But I have a love for warlocks so he's not getting replaced. I'm running a holy trinity and will do something different next group, like 4 hunters and a priest or something.