As an accompaniment to this update, an extensive dev diary has been released, detailing the entire process for a skill balance of this magnitude. There are three main factors that need to be taken into consideration when looking at which Elites to change: The skill has to be generally unused across all formats, all professions should have about the same number of updates and the skill has to be weak regardless of trends in the game. A skill that's strong as a counter to certain PvP builds but not others would not generally qualify, according to the dev diary.
Be sure to check out this complete dev diary for more information on the process and which skills in each class were changed exactly.
