Not to say that it isn't, or that it even is for that matter. I recently got Thunderlord out of a legendary engram (lucky me).I generally see a lot of negativity around SGA and good things about TL. I haven't unlocked its signature perk yet, so it's not at its full potential and i'm not in a position to properly compare the two.
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i use SGA for a reason it is my only exotic for now. it works good for me