Is there a single noun, preferably not a gerund, for the act of exceeding or surpassing? In editing test reports and similar technical material, I come across the notion of exceeding or surpassing a limit, threshold, or expectation. My dictionary searches have yielded only gerunds. I've considered "exceedance" but cannot find evidence that it is a word.
"Transcendence" might work for you, if you don't mind the minor New Agey connotations it can have in certain contexts.
The word I might use is overage. This usually refers to an excess quantity of goods, but could also refer to excess "performance."
A similar world in this vein is overachievement.
I think you could say: outperformance