The set bonus is 81 per stack, max 405 Haste at 5 stacks. It lasts 10 seconds.
The set bonus does not trigger from:
DoTs (although it will trigger from the initial damage of Flame Shock)
HoTs (it can trigger from the initial heal of Riptide).
Lava Burst, even when it naturally crits a target that doesn't have Flame Shock on it - presumably as a lazy way to cut out the use of auto-crit LvBs by Blizz.
Healing Tide or Healing Stream Totems.
cleaved Lightning Bolts provided by Primordial Wave
On the other hand, it does trigger from:
Any hit of Chain Heal or Chain Lightning - and it can gain more than one stack per cast from these spells.
cleaved Frost Shocks from Icefury. Like Chain Lightning, you can gain more than one stack per cast from cleaved Frost Shocks.
Thunderstorm, and can gain multiple stacks
Healing Rain, and it can gain multiple stacks from every tick. It does not trigger from the Acid Rain damage component though.
regular (white damage) melee attacks.
either hit (or both) of Stormstrike.
Any hit of Sundering, and can gain multiple stacks from a single cast.
Lightning Bolt, Healing Wave and Healing Surge
Chance to proc is very very high - it might even be 100% as long as the spell isn't deliberately coded to not interact.
TL;DR - works great for stacked healing with Healing Rain, and Lightning-focused Elemental builds, pretty decent for Enhancement, bad for Lava-Elemental builds
Happy to do any additional testing if anyone has any questions or suggestions for tests to do.
The set bonus counts as
two augment slots
So you cannot use this with (e.g.)
, but you can use it with non-limited augments such
Мешочек алхимических приправ
Кольцо с песочными часами
The set bonus is strong enough that in a few niche circumstances it can out-perform two augments, but generally these pieces are not worth the sacrifice.