by super...
Desent is an example of how non math factors effect the overall perception of game balance. The factors are not bad or good they are just qualities of the game.There are a number of factors at work. For example the extreme asymatry in player roles. Asymatry is counterd by reversing the roles and letting players use the tools that they feel have an advantage. However a descent campaign is played over many sessions without the player roles shifting.
the game is largely driven by scenario based victory conditions. Often victory is about understanding the solution to the puzzle first. If one side does not understand the puzzle of each new scenario a loss can feel totally unavoidable and unfair.
There is also the shifting of power level over a campaign and how a strong advantage may be earned if oneside understands how to invest their resources. Poor choices could really effect the Balance later Int the game.