All cards have strength's and weaknesses, that goes along with the decks as well. Speed decks can easily be countered, often by having the right shield/weapon/strategy. I think that game is pretty balanced as it is now, in my personal opinion, and am just looking forward to any new cards if there are any with this next update.
But as for Air, Water, and Light, a lot of decks are one trick ponies, or one trick done in various ways throughout the deck. Strategy is still a huge part of this game, and speed decks are a strategy. Building a successful speed deck isn't as easy as it sounds, it's just that a lot of people have discovered several useful combinations to create good speed decks. And on the opposite side, there have been many counter decks.
I still run your mainly basic rainbow deck, and many of the speed decks I come across overpower me early on. But I usually end up getting my stalling an defense up eventually and completely turn the duel around. A lot of speed decks deal with raw damage, or some way to defeat your opponent quickly, which leaves them lacking in various areas, like creature control, or defense, or perm control, and using the right combination, you can easily decimate a speed deck.
As for the dragons, I've never thought they needed a buff or a nerf and were alright as they were. I wouldn't want to see them buffed at all.
But stuffing a bunch of small creatures into your deck isn't always effective, like I said above about speed decks. Most can be stopped by the right shield, or heavily slowed down. Diamond shield would stop most of them, or weaken their damage. Permafrost shield or Turtle Shield do wonders, so does a Fire Buckler. Not to mention, with the right deck, Hope will stop basically all damage.
If you want to find out about the next update, you'll have to catch Zanz in the chat and hope he will divulge a little info on it.