This is how it goes for Necromancer pets:
Level 1-16 pets just about totally suck.
Level 20-39 pets're 'ok'
Level 44-49 pets are good.
Level 55 pet is very good.
Level 60 pet is awesome.
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About which pet-caster classes' pets are better? Well you gotta also ask "For which situation?" Assuming all classes are 60: Tanking: Animator Enchanter pets rule here. Versatility: Magician pets rule here. High damage dealing: Necromancer pets rule here. Best for taking crits: Shaman pets rule here... lol! :P
Shaman pets cannot compare to any of the pet-caster classes' pets, or else if they did, SoE made a huge mistake. Shaman's are to be known more for their buffs, debuffs, and're more healer than pet class.