Here in Australia, 250ms latency is awesome.

Most of us though are stuck around the 300-400ms mark.

The problem in multiboxing is it takes a bit of time for your slaves to realise what target your on.
I'm a tabber, i admit it.

I'm also 4 boxing warlocks.

Right, now back to the topic, how to use it to your advantage.

Split tanking (Hunters & Warlocks and possibly frost mages)
This is what this thread is really about, its very handy. A lot quicker than assigning targets and focuses and all that.
1. Click on 1st target and send pets in to attack
2. Quickly click on 2nd target and ur main pet will go and possibly another pet

Brawls
I'm a big fan of just pulling tons of mobs and spamming searing pain
Anywhere where there are lots of mobs close to each other (for me its western plaguelands)
1. Send pets in, other mobs aggro
2. Tab target a bunch of times and spam pet attack at the same time, then start spamming searing pain.

Chances are, most of your pets will be on different targets.
I'm using felguards so their cleave is helpful for me not getting aggro (searing pain is high threat too)