How to play:
It is quite simple... you use your hydra, then you run away and cast orbs.
This build is quite power hungry and has no damage to buffer when your power is out...
Because you'll find later in the game you really spend a lot more time running than you do actually dealing damage, and you will also find that using channeling spells will get you killed A LOT.
The beauty of this build is that all of your damage is AOE and all of your damage slows the enemy, while this build clearly has a lot less damage than many other builds... it is the best because it allows you to utilize much more INT heavy items and not rely on survivability in your items but rather know that you'll be doing plenty of running away.
Diamond Skin is there for fighting elites and champions, essentially if you somehow get nabbed by a wall, a vortex, a jail cell, or you somehow get cornered... use diamond skin to find another route in which to kite (usually this involves harry carry diving past the minions.)
I still recommend getting at least 15k hp (by 60), but having more is really not needed since the rune on Energy Armor stops you from ever getting killed in one shot... and you should be able to Diamond Skin out of any kind of damage past that.
Using this build I can easily solo hell with only items I've found... I've yet to use the auction house for anything but selling non-classed items and those items I replace, enabling me to accumulate quite the gold supply and still be able to do work.
While I've not ventured into inferno much (had one pathetic attempt to which I accredit my less than quality items [I'm just going to farm Hell some more with my new found Valor stacks till I can afford the very best items out there] ) but this build works and it works well.
With only 14k DPS you can kill Hell Act 4 Elites in about 2 rounds of Orbs if you aim well and keep hydra on them.
REMEMBER TO ALWAYS KEEP HYDRA WHERE IT WILL BE BLASTING THE ONE CLOSEST TO YOU. The slow is absolutely amazing in helping you kite and keep Diamond Skin off cool down. This does mean constantly recasting it while you kite-but its more than worth it.