In your case, use a shield (are you?). Use damage spells.
Against the assassin... I told you axe is not good except for shield cleave, because it is easily dodged. So unless you can get his dex down (or really cripple his strength so he is carrying more than max weight) you shouldn't use it much. Use something else he doesn't know, such as whip (which is not great, but is better than axe. Again, damage spells should do well because assassins have low hp in general. Of course, some will be exceptions because of gear.