After the last three updates (the update with minor card changes including improvements to ant swarm, blood vapour, water elementals, angry hornets, among others, the update introducing unlockable cards, and the one fixing fire prism), it seems to me that the feel of Spellcraft has drifted. In particular, I am finding it increasingly difficult to construct competitive decks without direct damage or other minion removal spells. I find this diminishes the game by reducing the variety of decks and discouraging defensive play styles.
Perhaps my perceptions are wrong; perhaps it is simply that I am encountering a different "generation" of players who are using different style decks. But I believe certain card changes and card introductions are a significant cause of the game feeling different.
Defensive styles of play require an ability to "handle" threats from an opponent's decks. Because there are so many possible threats, it is not reasonable to take a specialized card as a counter for each possible threat -- counters must have applicability against a wide variety of enemy plays and be useful in almost any situation. Until recently -- except against aquamancers -- a minion or barrier opposite a threatening unit would be sufficient (at least temporarily) to handle most threats. And those cards do have general usefulness. But increasing numbers of potential enemies have been given the elusive trait -- allowing them to simply flee to a different lane. Others have been given more defense. Enemy units like toxipedes or blood vapours surviving even one round can sometimes cause massive problems. And considerably more dangerous units now exist (fire prism turns previously innocuous units like pyromancers and chanting druids into devastating killers, while the new pyrosaur and gorger are cards with which one must immediately deal. And then cards like triton illusionist can pull dangerous enemies (e.g. deepsea thing) away from your blocking units. When dangerous cards cannot be blocked, they must either be neutralized (e.g. liquefy) or eliminated (e.g. meteor). Since only ocean and underearth have any real neutralizing options, minion elimination spells have become about the only viable option.
Right now, I am desperately hoping that the eventual introduction of the defensive mountain faction changes this; for now I am lamenting the loss of "old-style" play.
Whilst I can't say I've noticed any difference, I can say that Ice and Mountain both have strong neutralising effects, which may be more to a defensive player's liking. For example the Ice equivalent of Flamespike strips off the target's strength, rather than health.
Since the game can only be released in stages, due to limited goblin-power, and given the last sets were Jungle and Air, we might be in an 'aggressive era'.