There is no setting for what you are looking for, but targeting is really something you want 100% control over anyway. It's better to learn how to instinctively manage and align your casts with your group.

If you know a mob will go down before your cast completes, don't bother in the first place and start on the next target while everyone else is finishing the previous.

You can quickly cycle between targets by tapping L1 or R1 while holding L2 or R2.