Just so you know, Shard of Sacrifice does not remove your MAX HP.
I've taken in all of your thoughts and have decided to increase the cost and fix the ability a little.
Working on it now, tell me if you like it when I finish.
What if you have less than 100 max hp?
Say 97 is you max HP since SoV removed 3. They have you to 86 (random, but your health is 86/97 - 97 is your max HP now, and is the highest you can be healed).