Coming from playing a Warlock in WoW for several years, there are a few issues with pet control that I hope S-E addresses:

1) Separate pet GCD from player GCD. This is extremely annoying. When you're casting a spell, you can't even direct your pet to attack a different target. This also makes specific pet abilities less responsive as you can't activate them while the player is on GCD. What makes this even more wonky is that if you have your pet set to 'Sic' to auto-fire its abilities, it can do so regardless of the player's GCD.

2) If you set your pet to Passive mode, it should remain in that stance even after ordering it to attack a target. If the target dies, the pet should return to you. Currently, pets switch back to Defensive mode once you order it to attack. The reason Passive mode is preferable is that it gives you much more control over your pet.