For those who seem confused as to how something like this can happen.
The likely cause to this (since it was stated from the beginning of the intent, and later stated that there was a calculation for this), it is what is called code regression.
With so many moving parts, a section of code is tested, and confirmed, the tester usually moves on and tests another part of the code while development occurs. If a developer works on a section of code that impacts another area (e.g. combat calculations were being modified after the group combat code was completed), the developer working on the combat calculation could have made an error in removing or disabling something that was negatively impacting his calculations, without understanding the impact to it in another area. The tester, then going over the testing (regressing the change), goes over the areas that they have flagged for regression. When new regression areas are created, there is a chance that a specific use-case is not identified (high level/low level shared combat), in which case, something that was working as expected is no longer working.
Unfortunately, they do not have the time, or luxury of testing everything every time they make a change. They have to prioritize items, and identify areas of high risk. And many times, details that may seem large to us, are not as obvious during the testing cycle.
Understand, this is not an attempt to defend the error, simply pointing out that there are logistic reasons why errors like this occur. With how much they are trying to rush, they (the QA team) most likely are sacrificing a lot of regression time to focus specifically on development change testing. This will allow for many such regression issues. Most of the time, we as users will not know they are regression issues (they show up as emergency fixes typically performed immediately after an update, as the regression testing typically will run right up to the moment the product is released).
I hope this helps people understand better why this could happen.
Edited, Oct 12th 2011 2:50pm by rfolkker