Cant give u accurate information, havent played for that long yet. The grind is rather boring cos all the animations take so much time and its a big part of the game.
Variety of used cards, hmm, i think there are some staple cards in pvp cause of their power compared to their point value and some overly used spells and followers because they are just that strong or easy to use (no downsides, no requirements). But i do think that due to the low deck space there are quite a lot of different cards used. Lots of different factions, different win strategies, keeping dp low, having to put all the neccessities in there etc. Content is increasing quite fast i believe, cant be sure but pvp seems to be quite challenging (havent tried it out too much)
Well, some ppl are streaming this game so just watch them or wait for someone more experienced to post here.