Done 9/9 gold on my lock and hunter. With top world 28th scholomance
My opinion would be destro is the best. RoF/F&B immolate on trash, F&B incinerates/conflags build immense amount of embers, havoc shadowburn/Cbolt is amazing on bosses like Strife/Despair or whatever the bosses are called in Jade serpent.
Shadowburn sniping on trash before boss so you get 4 chaos bolts on bosses in a row is amazing burst and singletarget dps. However, I'd say all 3 specs are viable, depending only on what you play best.