Reduces the cooldown of your Reincarnation spell by X min and increases the amount of health and mana you reincarnate with by an additional Y%.
Improved Reincarnation is a Shamantalent in the Restoration tree. It reduces the cooldown of the Reincarnation ability, and greatly increases the amount of health and mana the shaman has after using Reincarnation.
Without the talent, the shaman will have 20% health and 20% mana after using Reincarnation. With two points in the talent, this is doubled. While the extra health and mana is wasted when Reincarnation is used for wipe recovery, it increases the viability of using Reincarnation to get back into the fight while the group or raid is still in combat. This makes the talent useful for raiding.
You can equip the Totem of Rebirth right before you die to decrease the cooldown of this ability by 5 minutes (this gives a 10 min cooldown on Reincarnation).