[andrewas]

NO, haer'dalis is not neccesary to complete the quest.

For the second point, salamanders can be hurt severely with cold/fire (for fire/frost salamanders respectively). ALso a decent level Tank (Tank as in rock hard fighter, not an actual tank) should be able to take one in melee. To take the mage open up with all your missile weapons and dont let him get any spells off. Cast Magic Missile (Newbies often overlook this spell and assume its useless cos its level one. This is a mistake) to get past stoneskins.

You might need to level up, theres no penalty for leaving the quest and coming back later.