Mind Soothe reduces the aggro radius of a target mob, which means you can tactically avoid pulling certain enemies. This is very useful to skip certain pulls, or to run through certain areas without drawing enemies, and thus comparable to a targeted version of stealth in some situations. Beware that if the mob resists Mind Soothe you will aggro it and enter combat. Using Mind Soothe on players of the enemy faction is an aggressive action and will cause guards of neutral cities to aggro.