Show me the broken, overpowered cards here.
First of all, the "broken" and "overpowered" words were used here with a little exaggeration. The problem is not that the cards are broken as a single, but the overall system tha makes them broken. Upgraded rare shards like Shard of Divinity and Shard of Sacrifice are not very powerful if used once, but filling your deck with 6 SoSa and 6 SoD makes it really overpowered. Shard of Sacrifice is okay to block you for 2 turns (or even 4 turns) and replace your damage with healing, but if abused and used 3, 4, 5 or 6 times in a game it makes healing for 6, 8, 10, 12 turns which is rediculous. You don't except anyone to have Shards of Patience or Sundials or Antimatters to prevent their creatures from attacking or healing their SoSa opponent, do you? And since 99% of decks need to deal a great amount of damage with creatures each turn in order to win, there always will be lot of strong creatures to heal you. What's more, Shard of Divinity can be used to both heal you and to extend your max health, making it excellent supplement for SoSa (just don't use them when SoSa is activated).
Shard of Void is not overpowered, since it doesn't inflict great "damage", same goes with Shard of Gratitude, since it doesn't heal you so much and they are both permanents, so they can be dealt with PC. However, a lot of them together provide too much "damage" or healing and since they stack (something that other permanents like Bonds and Sanctuaries don't do) they can protected by a single Enchant/Protect Artifact. One or two SoV or SoG is not something broken, but, like the other two shards, they become ridiculously powerful when lots of them are out there, especially if Enchanted/Protected.
The fact I like in Elements and which I didn't found in other TCG (like MagicTG or Yu-Gi-Oh) is the lack of powerful ultra rare cards with which you can fill your deck and defeat a much better player than you just because you have a broken deck while your opponent has a normal one. Elements is the most balanced TCG I know, but if decks like this keeps coming, then Elements will slowly but surely lose its balance and it will become another I-have-a-deck-full-of-broken-rare-cards-so-I-win card game. I don't want to see Elements becoming like that...