When tanking mobs with your Voidwalker, save casting Immolate until the end of your DoT rotation. Not only does it have the shortest duration, but as it deals initial damage, it generates the most threat and could possibly pull the mob to you.
Immolate’s periodic damage has a 50% chance to generate 1 Soul Shard Fragment (was: periodic damage has a 15% chance to generate 1 Soul Shard).
Immolate’s periodic damage critical strikes have a 100% chance to generate 1 Soul Shard Fragment (was: periodic damage critical strikes have a 30% chance to generate 1 Soul Shard).
Hotfix (2016-09-23): "Immolate damage increased by 11%."
Hotfix (2016-08-16): "Immolate no longer has a chance to generate a shard on its direct damage."
Patch 7.0.3 (2016-07-19): Now has a 15% chance to generate a Soul Shard (double on critical strikes). Direct damage increased by 162%, damage over time increased by 42%, duration increased to 18 seconds (up from 15).
Hotfix (2014-12-15): "Immolate's damage has been increased by 8%."
Hotfix (2013-09-23): "Immolate's damage has been increased by 30%."
Patch 5.4.0 (2013-09-10): Damage has been increased by 10%.
Hotfix (2013-04-18): "Fixed an issue where targets of Havoc were receiving more damage than intended from Immolate."
Patch 5.2.0 (2013-03-05): Now deals 15% more damage.
Patch 5.0.4 (2012-08-28): Now a Destruction specialization ability. Cooldown reduced from 2 seconds to 1.5 seconds
Patch 4.0.3a (2010-11-23): Damage has been reduced by approximately 12%.
Patch 4.0.1 (2010-10-12): Now burns the enemy for 677.42 Fire damage (up from 460) and an additional 2150 (up from 785) over 15 sec. Only one Unstable Affliction or Immolate per Warlock can be active on any one target. Mana cost 8% of base mana, down from 17%. Range now 40 yards, up from 30.
Patch 3.3.3 (2010-03-23): The damage-over-time component of this spell can now produce critical strikes.
Hotfix (2009-04-15): "We have hotfixed the damage of the Warlock spell Conflagrate from 100% to 70% of Immolate's total periodic damage instantly. The tooltip may still show 100% until a future update though."