Once you have AoEs, you should use them on trash while auto attacking the target with the highest health. Any time you are using single target attacks, make sure you are constantly adjusting your target so that you are attacking the target with the most health. This will help the people who are AoEing by avoiding one or two mobs still having near full health when everything else dies and will ensure you don’t interrupt their casts by killing their target. Don’t bother using Assist Target on the tank, as the tank should be spamming AoE and auto attacking the highest health mob but most tanks are bad and won’t do this.