As I see it the general opinion about ALL pet classes is, that they really could use some pet AI and quality of life improvements.
Here is a list of changes I would like to see. If someone has better (or easier to change) ideas, please speak up 
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Use the same AI for all pets / minions and just adjust numbers like damage, movement speed, life, attack speed and so on accordingly to type. So it is easier to improve overall minion AI (I play a necromancer c2 and it feels like my pets all behave differently). Preferable take the companion AI so that all pets teleport to the player at certain range (this would already help very much ;))
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Make Tree Root Crystals, Traps and similar obstacles LESSER targets. So that pets would only attack those if ordered (via Dog Rush for example) or if there are only lesser targets left in attack range.
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Improve pet surviveability balance. My idea would be to just give all pets a certain amount of blocks, like Quarrel Shooter’s Pavise or Necromancer’s Corpse Tower, instead of life. This would make the durability of pets much more stable. Right now bosses just one shot many pets and against weak monsters the same ones are nearly invincible. This would help a bit against afk pet bots too, since the pets would even die to the weakest monsters eventually.
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Let us decide our pets behaviour. This would require more work but would be a huge quality of life improvement. My idea would be to implement three buttons in the companion tab which influences all your pets (yeah nothing really new here :D). One that lets your pets attack enemies that attack you, one that lets your pets attack enemies you attack and one that lets your pets attack everything in their sight.
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Better targeting for pets and pet skills. Maybe let hits count before the attack animation shows. As it is right now moving monsters cause a lot of missed attacks (stumbling pets and wasted cooldowns). It is a problem for many skills, not only pet related ones, though. At least let skills like Coursing attack the enemy you are targeting or attacked last.
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Let pets not be targetable by players. Instead there could be a key command to toggle pet life bars on and off. Right now pets can block off npcs and other activation spots and make targeting in mouse mode difficult. Interaction with a companion could happen via a key command or the companion tab.
