Rare units are no fun, I hardly can imagine any case that they would be fun. I just played a 3k game and I got 11 9 attack 9 defence units in second turn, I just allied everyone to finish this nonsense, I think you should change the default to no rare. And btw I think premium have much higher chance of getting rare units, personally I didn't see any non-premium getting rare which makes the whole thing even worse, we have generals, we have better upgrades, more strategies and more chance to get rare units, this makes it p2w game. I know this is not always the case for higher ranks but low ranks will always get rekt by premium players.
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"I am not afraid of an army of lions led by a sheep; I am afraid of an army of sheep led by a lion." - Alexander the Great