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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Plus, Thunderlord -blam!-s on arc burn. IMO generally your best use of an exotic slot with arc burn, whereas with solar burn you have several better options than SGA, like Icebreaker, Vex Mythoclast, or gally. The only exception being Patience and Time in some situations.