Greetings.
I've played this game for over a year, maybe two, even; I can't say I remember exactly. At a time, I took a break and I returned recently. I was pretty convinced that I used to have an account on these forums as well, but apparently it does not exist anymore. Regardless, I experienced several things upon coming back, and whilst I do not know whether they are intentional or not, I thought it couldn't hurt mentioning them.
Namely: pretty much every deck I ever encounter in the Arena is some variation of a rush deck. It seems that game balance has been tilted very tremendously towards them. To be more specific, the vast majority of the decks falls into one of the following categories:
1. Graboid rush: One of the most irritating decks I've ever encountered. Not only it dishes out huge damage in several turns. It almost always has some Earthquakes, most usually several of them right in the first turn, effectively depriving the player of any means to generate quanta save for Nova and Immolation. It also has some Reverse Times, so that even if the player somehow, by some weird twist of fortune, manages to play any creature on my field, it is immediately returned to the hand.
2. Phase Dragons with Shards of Wisdom: Just as annoying as the one above. I must admit, though, that this is due to a single card; I think that Shard of Wisdom is pretty much a gamebreaker now. If the player keeps out an ordinary shield to defend against the dragons, they get the shard to deal spell damage. If the player gets a Reflective Shield out, then the shard is simply not played. Not to mention the issue that this actually requires the player to use either Life or Light quanta, which is not really an issue for me, as I do, but it might be to others. It's quite difficult to solve anyway, because the +4/+0 bonus the shard grants can easily build up to ridiculously high values; I have seen 26/8 Elite Phase Dragons, even. Or, if I happen not to have a reflective shield around, then I happen to encounter three or four 12/8 Phase Dragons with spell damage.
Ghosts with Nightmare: Also rather unmanageable. These can very effectively lock down a player. First by stealing some permanents, which others can do, no big deal; but they don't only prevent drawing new cards with Nightmare, and punish the player for playing cards (by filling their hands with more and more ghosts until they are the only cards available), but also cast Reverse Time on any ghost the player has somehow managed to get on the field.
Generic Fire rush: One of the more tolerable types, though defence against it is still rather limited. As in, usually it immediately destroys shields or weapons capable of creature control, or uses Rage Potion or Fire Lance to destroy creatures with such skills.
Rainbow Rush: At least these are more varied than the types above, but they all have something in common. Basically a Mark of Entropy with loads of Supernovae, Lava Destroyers, Forest Spirits and Phase Recluses. Basically in the second or third turn of playing I usually meet with a bunch of creatures which deal very considerable damage on their own. Also, Shard of Focus. Yes, it is still an issue, I think; in some rainbow decks, it has gone entirely crazy. At least it's not really a nice thing when the AI plays Fractal on it, and in several turns I literally have no permanents, and should I play some of them, they are immediately destroyed. Also, very similarly to Earthquake, this card can ridiculously easily lock a player down entirely. As in, if it gets played early enough (which isn't that difficult, considering that the upgraded one costs no more than four Gravity quanta), then it destroys three pillars (and considering that I usually have no more than two pillars in my starting hand with almost one third of my deck consisting solely of them) and then it turns into a Black Hole can very easily leave a player completely unable to play anything.
Long story said short: Basically all Arena decks now focus on either getting creatures out in several turns and overwhelm the player before anything could be done or they rely on complete lockdown. Or both (see Graboid rush).
Edited part follows:
I'm sorry for having to edit this, but I had to leave urgently and I have just returned. To finish what I intended to elaborate on:
First, there are some other deck stereotypes that I did not mention. Such as the Darkness Devourer-Steal combination (complete deprivation of quanta, a bit more tolerable than the above because takes a bit longer to set up), the Gravity total lockdown (very nasty... Shard of Focus, add something for damage and the opponent doesn't really stand a chance).
