Its just as good burst, sometimes even better with the sustained damage you can put out with combustion. It requires better skill and longer setup tho. Works best with a healer in 2s or a dot dps like sp or lock. 3s wise i'd run with dot cleave or rmp for heavy switches. Its not a zerg spec since you dont have the controlled burst frost has plus u rely on novas for deeping your kill target which can be annoying if they get broken by damage. Definatley viable tho and hella fun in bgs, just takes more time to learn than frost imo. Hope that helps mate.