So If any damage by first strike kills your opponent, the games stops, This is major drawback after spending a lot of time building up your army. You expect the opponent to go to -400 but he dies at -1 because some small creature did first strike damage.

Please, if you see that the game is over, allow excess damage and don't stop the game after the first blow that makes the opponent go below 0. Since this changed the game is less fun :)