Shadow Bulwark

I dont know if anyone else has heard it, but when you cast this, one of the things your VW will say is I...am...void...where prohibited...

This is an incredibly useful spell while grinding, especially in early contested zones like Hillsbrad and Arathi Highlands.
You wouldn't believe the number of times times that, after fighting a large group of enemies, I've had my voidwalker cast this to heal himself and accidentally revealed a rogue/feral druid getting ready to jump me.

The automatic use of this ability at 20% is pretty worthless since it doesn't heal for the increased amount.
At 50 it has 6006 health for me right now (with my 429 stamina), so an extra 30% max health would bring it up to 7807. At 20%, it'll go from 1201 to 1561, essentially a heal for 360, which is only about a 6% heal.

When doing big pulls, use this near the beginning of the fight.