at begining of act 3 merc. help

i seem to have hit a brick wall and can't progress. my ability to tank is decent but hardly enough vs the stronger damage monsters but i can't seem to do anything close to decent damage. every enemy that is resistant to fire just takes too many hits to kill. even white enemys can take up to 6 hits to kill when I'm going all out. any advice on how to fix my damage situation would be helpful. my spec is and my gear is
my strategy is to curse with flammability, toss fire traps and then start laying down infernal blow. cleave and heavy strike just don't seem to do any damage and hence anything with high resistance just takes forever to kill.