The Nate Dragon grind is just boring and not fun. The end of the world should be available at level 125 at the latest or even level 100. If you want to keep the game the same length try to stretch out the mid to late game. I basically skipped over Fire Phoenix and Thalia on my first play through because I could get better stats with other Crusaders.
Just had a game where I ran out of cards with 2:30 remaining and won because the opponent didn't play anything either. Pretty boring waiting it out though.