Self Levelling - 1 High & 3 Low Characters - Sweet Spot?

As the title suggests I'm looking for a sweet spot to level my own toons by multiboxing. The way I plan to do this is by playing one high level character while the other lower ones follow, anyone know a sweet spot where I can get as much xp/h whilst the dying chance is pretty low?

I leveled my barbs in arreat crater, from 10-60.

I used an archon wizard to lvl up 3x toons in The Keep Depths Level 2. The reason why I didn't go for arreat crater, is the worms that one shots your toons all the time, and all the spears and range attacks in the area.

Best results I've achieved so far was last week during the 1 year D3 anniversary buff with a level 60 Witch Doctor using Insect Swarm in Keeps Depths 2 (best spot). Insect Swarm is easily the best skill I've used so far for powerleveling; you cast it once and everything dies since it spreads automatically. You get decent kill counts too for added exp. In the past I've tried Archon, throw barb and multishot DH but it wasn't as fast.

I also had dogs and the gargantuan to distract mobs and protect my low level chars since in Hell MP10 killing mobs was a little slower.

Lvled a wiz 1 to 60 in 6 hours doing the whymsy runs. My main is a 350 dps wiz shooter for the runs

at lvl 14 ad a leoric ring and a rs ruby in helm.

23 go with cains + laerics and ruby the rest of the way.

25 got to night mare and 50 go into hell and finish.

If any one does it faster elswhere post it and let us know.

Whymsy always bee the default lvling place for hard core.

By the way she is now a comperable cm wiz with my main and its awsome running 2 cm wizes together mp8 +

Did a new personal record from 1-60 in 2 hours and 20 minutes with the following:

1-30 -> normal dungeon keeps 2
lvl 30 -> kill diablo
30-50 -> nightmare dungeon keeps 2
lvl 50 -> kill diablo
50-60 -> hell dungeon keeps 2

This was only done with 27% exp gem in helm and cain set.

I am going to try this spot right this instant! Thanks for the tip guys!

You can actually go into nightmare at lvl 25 which i recommend as its so much faster 25-30 than staying in normal KD2.