i am a level 7 player and have already killed 3 frost trolls. I use frostbite spider's poison on my orcish handhammer and beat the crap out of them. Use relenting force, then couple of hits with orcish handhammer, then paralysis poison, couple more two handed shots using stamina and again unrelenting force to put it out of balance. If you have a helper, it is even easier.