The stats do sort of explode during Act 2, but on the bright side, the challenge of the game doesn't immediately become trivial like it did in OS1. I think the overall design of act 2 is pretty fine, and the way the stats are balanced is probably necessary to keep things engaging. Every level needs to be a percentage increase over the last one rather than a linear increase from the beginning or else it quickly stops mattering. I would prefer if the power curve were more level-based and less gear-based though.
