I'm guessing we're using the word balance to mean two different things. I'm not actually sure how you're using it, sorry. I can't connect Cyseal's open world freeform structure with imbalance. Balance doesn't imply a controlled corridor-like game experience, like your comment seems to be suggesting.
It is being used in different ways.
The "single player game doesn't need balancing" argument is talking about overpowered mechanics being rebalanced so that they are no longer overpowered. This is unnecessary because the game is not competative and players can (artificially) limited themselves to not using those mechanics.
Noaloha, you make some excellent point but I think you're ultimately talking about game design in general, which includes balancing towards providing a certain kind of experience.
It seems to me that individual changes in the former category will effect the overall game design (which you refer to Noaloha), but will not be sufficient to achieve the latter's sense of balance (ie Cyseal vs the rest of the game).
Addition: I still think the easiest and least disruptive way of improving the challenge of the game is to allow the AI to go first in combat. And I think this would be achieved, in most cases, with removing the Initiative bonus from Leadership.
