It's pretty good, yeah, but I use a slighty different one.
http://eu.battle.net/d3/en/calculato...dTY!YeU!acaYaa
However, for that specific fight I would recommend this build:
http://eu.battle.net/d3/en/calculato...dTY!aeU!acZYZa
Firebomb to trigger Vision Quest and for the adds.
Spam the boss with bears until you go out of mana.
Save Spirit Walk for when you really need it to avoid damage.
Use Soul Harvest smartly on the adds such that to get as many stacks as possible.
Your pets should always be off-cooldown when they die and make sure they are not on cooldown when you start the fight.
Spirit Vessel is a life-saver, Jungle Fortitude helps if your resistances are not high and Vision Quest is needed to help with bear spam.
Note: Keep in mind that when the Gargantuan enrage ends, if you re-summon it while it's alive, the new one will enrage again
You can do this to get a boost at the start!