There are more ways to discover 'imbalance' then just stumbling across them in regular play. Many games have 'theory-crafting' communities digging into the numbers outside of actual play. I used to love reading through D&D rule books, even though I didn't play it. Now unless there were inherent time sinks that prevented zergs, if there were any serious imbalances, one side would roll over the other in far less than 1500 hrs.
