Shard of Focus seems too powerful to me. It destroys 4 permanents over 4 turns at minimal cost. In addition, if you combo it with cards like Aflatoxin, you can damage it and reuse it. Shard of Focus actually combos extremely well with Grey Nymph, of all things :p (unless the hp refers to max hp of the shard and not current hp, in which case my combo doesn't work) Even just as a delayed Earthquake/Quicksand, this would be sick, and it should get a cost increase in part because of that. Play it turn one and bump their towers off as they get them. This would also combo extremely well with eternity, allowing unlimited use. Do we really want -every- deck to be scared of playing all their towers turn 1, just because someone might have this card?
I can understand the need for permanent removal that is accessible to all elements, but this is too strong. Perhaps if it only destroyed one or two permanents, and had a similar one turn delay like it does now? 0/10, +5hp and destroy a permanent, die at 0/20 and give a black hole? I do like the idea of making it a creature, because that gives more ways of countering it, like lobotomy or damage or basilisk blood or whatever.
Another thing that could be done is to make Shard of Focus destroy opponent's permanents, but at random, so you might just destroy pillars, but you can still at least have a chance to destroy their shields and other important things. That would probably require a rename, though, as that isn't particularly fitting with 'focus', but it would make for a more balanced card, although it still suffers from the pillar destroying problem at the beginning of the game, with that low other cost.
If random is unappealing, it could work off casting cost, and destroy the highest cost opponent's (nonpillar/pend, to avoid overshadowing earthquake) permanent each turn for a few turns, like 2. That way, it would be predictable, and somewhat counterable (playing a graveyard to save your skull shield, etc) In case of ties, the shard's owner would get the choice (or it could be random) and it still couldn't touch PAed cards. I actually like this one the best, I think; make it destroy 1-2 nonpillar permanents, maybe +1 if your mark is earth, and have it pick the most expensive targetable nonpillar permanent your opponent has. This gives it use without turning it into an overpowered colourless earthquake/pulverizer, and makes it harder to combo with eternity. (you still could, but you'd have to activate eternity more often to keep it going than if it destroyed 4 permanents, and it would be more quanta-intensive than pulverizer)
If you wanted to keep people from using eternity on it, a counter could be that if shard of focus were rewound, it would turn into a random shard (or permanent) kind of like skeleton does now for creatures. That has no thematic justification, but it would add an extra dimension to the card, though it increases the complexity, which is bad, especially as everything I've suggested already adds to its complexity.
The aether shard seems balanced to me. It requires you to have a lot of them to get a useful effect, but if you do have a lot of them out, it's very strong. If someone plays one or two of them, you won't even notice, but if they get to three, you're going to feel the pain, as being capped at 10(8) quanta will make a very appreciable game difference to most decks. With two, you'd be at ~18 for a cap (depending on how rounding is handled; I'm assuming 75-37-18, but you could round up and go 75-38-19) and that's enough to affect a few decks, but not too many. The math with 75 happens to work just right (possibly zanz-intended!) such that you need four of these to get them to the minimum of 8. (or 3 to get them to 10, regardless of whether you round up or down in both cases)
Sorry if this is somewhat disjointed, I kind of added stuff to the middle as I went along :p Short version; earth shard OP, aether shard is about right.