I'm a life wizard and I can say that that has never happened to me or anyone I know in any dungeon ever, so probably not. I think critical block has to to with offensive attacks and not heals. Hope this helps!
If you're casting sacrifice, you can critical and then block the attack on yourself, but whoever you were healing still gets twice the extra health. Healing cannot be blocked :)
i know its silly and i have been playing this game for almost almost 6 years now but i just wanted to know to be 100% sure and also i just wanted to post something