It seems as if the game is not without a sense of irony.
Recently I've been posting (complaining) about the rewards of a tier VI sacrifice being insulting (specifically 2 skill shards).
Well, I was very close to another tier VI sacrifice, and with the blue rescuer coming up I really could use the 50 rare soul reward.
I was just a little short, but luckily for me I had almost completed a vortex fill - that would probably get me enough essence to reach tier VI.
So, I fill the Vortex and get ...
7 skill shards.
Well played.