11/9 threshold? I don't know what this means. If you are talking about total dmg per turn, then that doesn't even matter. You don't wait until your opponent gets out a big creature. If your opponent has out enough damage to give you back enough hp to play another shard after the first one runs out, then that is all you need. Either your opponent continues to discard their creatures, or play them and heal you up faster.
But unless a person can get out the 3 turn win deck (red dragons), you're not going below 40 hp within 3 turns. Even lava destroyers will only get you down to 50 something hp in the 2nd turn. But if you're not playing against either of these decks, you usually have at least 2-3 free turns without getting close to 40 hp, and 32 hp will give you usually 3-4 free turns, and again, don't wait to play the shard, play it early, itll buy you time to get out a good combo.