I agree with Hands-o-death, get rid of the shard bag, space is to precious, and keep 4 or 5 in a regualr bag. If you use a shard, just make sure you replace it with your next mob. It's easy enough to do, and you'll make less trips to the vender. Soulbags are dead space, and if your timeing is on, you can pull a shard when the mob is down under 5% without wasting mana or actual casting time. The only time you may need a few more shards is if you going into a lwr lvl dungeon with mods that won't generate a soul, and your with a bunch of noobs that don't know how to keep from wiping! But that situation will probably be rare, and you'll have time to prepare.
Of course, you can always get the Lock add-on to manage your shards, and then drain every mob out of habit. The Add I use lets me decide how many shards I want to keep in my bag at any one time. I keep 5, the rest are destroyed unless I choose otherwise. So, shard management has become a thing of the past.
I'd rather see Blizz focus on something a little more thrilling than "Shards", like perhaps, a quest to get a feldragon or a Dreadwing...flying mount.....lol....HEY!...stop lauphing..it's OK to dream!