What method do you think is best for figuring out ones god-tier aspect? I've taken various quizzes but, a sylph or rouge of doom doesn't really seem like me...

Introspection, really. See if you resonate with the personality or story of one of the Characters in Homestuck, with their power sets… Check the Classes and Aspects individually to see if there’s any of the descriptions you think fit you the most. Ask your friends too what they think about you and what Character they correlate you with the most! But in general, the only one that can truly decide your Class and Aspect is yourself.