I hate searching for information on the instances while I'm in one for the first time. I haven't found many guides out there yet with good information on the dungeons themselves, it's super frustrating, and trying to shuffle through a bunch of threads just to find the information... Hopefully this will help out!
Sinestral Manor - Level 26
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Cultist's Refuge - Level 35
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Necromancer Tomb - Level 41
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Sigil Adgstringo - Level 45
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Golden Labyrinth - Level 48
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Saleron's Sky Garden - Level 53
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Suryati's Peak - Level 56
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Kelsaik's Nest - Level 58
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Balder's Temple - Level 60
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* Fane of Kaprima - Level 60
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Ebon Tower (Hard Mode) - Level 60
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* = Recently Updated/Added