Don't discount that Astral!
Personal Luck is an absolute necessity for it to cast before mixing it up...
Blood Vengeance (which is the main reason that the Vastness is so beloved) works when units
try to hit the Vastness... so it's obviously best to be attacked and not get get hit!
This is especially fun with large amounts of javelin throwers/archers as they explode in a puff of blood halfway across the battlefield...
I also like to cast Astral Shield and Resist Magic before heading in... but you don't want too much fatigue before he heads in to fight. (I found this out recently in an MP game
)