Mage pet questions.

[Obsidus]

I've always wondered, what are each of the Mages pets good for? As far back as I can remember I've only ever seen and heard of Mages using the Fire pet for dps in groups and soloing, and the Air pet if tanking a mob was more important that killing it quickly (due to high dodge + stun proc making it actually take less damage than the Earth pet while hitting for more).

Is this even remotely accurate? Do the Water and Earth pets literally have no role? If someone could give me a rundown on when/when not to use certain pets and what they're good for I'd be greatful.

Another thing is, while using the search feature to see if this had been asked before, I found a thread talking about pet aggro being complete garbage (things like the player hitting the mob once for 1 damage, then backing off and having the pet hit the mob 3 times and ostensibly taunt twice and yet STILL not pull aggro off the player). Is this still true? Thanks in advance.