The tooltip is somewhat misleading, and the talent is much better than it might seem at first glance. It has a chance to trigger not only from the attack that brings the shaman below 30%, but also on any attack made against you while your health remains below 30%. Against a fast-attacking opponent like a Rogue, it is effectively guaranteed to trigger any time you are below 30% health. The effect has a cooldown, however, and cannot occur more often than every eight seconds. Only hits that actually trigger the heal will cause the talent to go on cooldown.
Nature's Guardian is entirely passive, and will work even when stunned or otherwise incapacitated.
The threat reduction effect reduces your threat by roughly 10%. This is rarely sufficient to make a difference, especially since it doesn't trigger until you are already at very low health. The talent is normally taken solely for the healing done, and the increased survivability that it offers. It is especially useful in PvP and arenas, and is generally considered to be a key talent in any PvP build. In PvE the talent is much less useful, but can still be very helpful on certain raid encounters where everyone in the raid takes a lot of damage.
- Patch 5.0.4 (28 August 2012): Now available to all specializations as a talent.
- Patch 3.2.0 (04-Aug-2009): Redesigned. Now has a fixed 100% proc rate, has a 30 second internal cooldown and increases the shaman's maximum health by 3/6/9/12/15% for 10 seconds.
- / Patch 3.0.2 (14-Oct-2008): Cooldown increased from 5 to 8 seconds.
- / Patch 2.0.1 (05-Dec-2006): Added.