Seems like a card that is meant for very specific combos, such as boneyard/oty/skeleton or viruses and other various heavy sacrifice themes. Besides those specific uses it seems like a rather marginal card even stacked. Granted, it would be killer with an unstable gas/afltoxin/condor combo, but once again it becomes very specific.
Maybe I am missing another aspect of its potential though. Just food for thought.
Think of it this way. You're playing RoL/Hope, and suddenly your opponent rain of fires, and kills almost everything you have. You, fortuitously, have 2 Shard of Fortitudes in play, so you gain 2x* amount of life, and skyrocket back to full health. Your hope is now useless, but you got a free heal (albeit one that took up multiple cards in your deck) to continue your battle with.
Alternate scenarios. You have 4 Shard of Fortitude in play (you're playing a stall rainbow), and your opponent's Pharoah's are starting to get in gear. But now, your opponent has to decide if devouring your creature is really worth you gaining 4 life, whether he needs that creature off the board or if he needs that extra toughness on his scarab, or whatever reason.
It's fairly balanced, for the low cost of 6 cards in your deck, and 24 random quanta, you can have a miracle to keep you in the game when your opponent finally gets board control. Or you throw it in to your stompy decks as a little extra CC protection/EM possibility.
The possibilities are endless. The question it poses your enemy is: is it worth it?
Will this card be abusable in the right deck? Sure 'nough, it'll probably be fairly potent (but still posing the concerns of early game quanta consumption, more combo to work out drawing into, and less deck space) in the right sacrifice oriented deck.
Will this card be solid when you aren't trying to abuse it? If you're playing creatures, and suspect your opponent has creature control, undoubtedly yes.
