Certainly, most of the time it’s what you want. But not always. Perhaps it’s important that Legacy takes a certain amount of damage, so that he’s the target with the lowest (or not the highest) HP. Perhaps you’re targeting him with Fanatic to keep Zealous Offense active, and you need to do more damage. We can’t predict the strategies that you’re going to use, and so we need to make sure you always have control over the outcome.