These are all valid arguments, but the fact remains that built-in macros would generally be more viable for the less perceptive of players. You make note that there are distinguishing factors between different levels of players, but the reality is that you will not always have great healers. I would much rather have a player who is not comfortable micro-managing their pet who is still capable of using their pet's abilities via a better-designed UI or macro system. As for the tank-following argument, setting the follow command on someone doesn't necessarily put you in harm's way, depending on the range. This would obviously have to be taken into account when designing a suitable mechanic.