You know you've got a problem when you can't beat the final boss after maxing out every character AND purchasing the max level for EVERY rune. The levels beforehand are a challenge without the runes, but once you max out on runes they become a cakewalk. Then you fight the final boss, with an overshield that you need to down before even damaging him, a ground blast attack that fires off so fast that there is no point in having indicators, and will randomly summon massive waves of enemies that take several hits to kill if you're lucky enough to get a wave with no minibosses. Later he starts summoning waves faster than you can clear them, and it becomes a fight against your own allies' AI that go full retard because there are more than a few mobs on the screen. I was enjoying this game, but fights like this with crazy artificial difficulty spikes that make no sense and are there for no apparent reason are a major buzzkill, especially for something that is required to complete the game.
Grolox: I see your point. While MtG does have the forced limit on mana, there are MANY options to get around that. Exploration for example lets you play two lands per turn, as do many creatures, and the Landfall mechanic only encourages this. Also, creatures like Kruphix, God of Horizons and Prophet of Kruphix literally eliminate the problem you bring up by eliminating mana emptying and allowing you to untap lands on all turns respectively. Not to mention that Prophet gives creatures flash, which encourages creature summoning, not only as a board population mechanic, but also in response to attackers, furthering the finesse involved in combat and otherwise, which is lacking in this game.
I get the premise, and as a veteran of other card games (MtG, Pokemon, YuGiOh, etc), I can see where this game probably got some inspiration. Where I feel it really falls flat is in the damage exchange mechanics, though I will admit that I am biased after many years of playing Magic. This game appears to pretty much be "summon all your creatures and let them steamroll your opponent, and maybe throw in some damage spells" whereas in Magic, for example, combat is more "summon monsters, then decide whether or not it is profitable to attack, because your opponent could definitely block and kill your monsters." While the gameplay itself is pretty fluid and simple, I can't say I'm a big fan of the game as a whole.
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