First of all, this game is now neither pay to win, nor unbalanced: reviews which say so are usually pre-Griffin Bane expansion, which immediately gives new referred players all six starter decks, plus tons of gold to buy cards upon completing the introductory campaigns, and brings back all Factions to competitive levels.
More complex, varied and ultimately satisfactory than Hearthstone, this game has very nice mechanics, with the board consisting of four rows and two columns (shooter and melee) for each player, spells which can affect single creatures, specific areas (squares, rows, columns) or even the entire board, and fortunes which usually manipulate cards and decks.
Creatures can be basic or have a lot of useful abilities (immune to retaliation, stackable, outmaneuver, etc.), including "enter the board" effects.
Simply put, this is the best CCG I've ever played.
P.s. Since I love the game, I'm glad to help new players to understand it, so feel free to ask for help and/or for my referral code, should you have no friends who play the game.