Well in EQ1 i've got a Necromancer as my main, and if EQ1 is similar to EQ2 with pets then it should go like this:
At lower lvs you pet is more like some extra damage that can't tank very well. When you get higher you pet becomes much much more powerful and can tank pretty decently.
Your pet has a class. This does determine it's tanking ability and damage output. If it's a rogue then he can't tank but can do great backstab damage. If it's a Warrior, then it can tank and in really high lvs has a built-in damage shield (you take damage if you hit it... don't know if you have that in FF or Star Wars)
Necros can do nicely without a pet, but I always have mine out.
Im planning on getting EQ2 (and I am not quitting EQ1) and I plan on making a Necro since im already used to playing one. If I don't get a pet at the beginning then im going to keep playing anyway untill i do get one.