The value of shard of bravery can only be explained in a context. I believe its true value comes from speeding up rushes and finding combo cards. Examples of decks that use it are voodoo bravery, debauchery, dazzling dolls and golem rush decks. You can find all these decks on the forum.
Shard of bravery is used when you think that drawing cards is more important for you then for your opponent. A reason for this could be that you play a fast deck while your opponents deck is slower. Rushing is a strategy and shard of bravery fits that strategy.
Pillarless debauchery is an example of a deck that uses it this way. Your deck tries to chain cremate damselflies and minor phoenixes into serpahs and rush your way to victory. Your opponent will not be able to get his entire hand into play, which implies the oppnents didn't get to make use of all his cards. The extra drawn cards had less value for your opponent.
If you used the bravery shard on the final turn the bravery shard has a one sided effect. You also create an advantage when you combine silence with shard of bravery.
Other phoenix rushes and air decks can also use bravery shard for similar reasons.
The ultimate is a shard golem deck. It tries to rush people down, but bravery shards also grow the golem. The value does not come from card advantage.
Voodoo doll decks use a combo and they need to find all the combo pieces. Voodoo bravery needs to find its combo in time and doesnt deal any damage until enough combo pieces are found (doll+pull+blood). Dazzling dolls needs to draw almost its entire deck to find all 8 combo pieces. Without shard of bravery its almost impossible.
The point I'm trying to make is that the value of bravery shard is useful for rushing and finding combo pieces. I don't think it should be played for card advantage.