1) Don't be afraid to use your single-use items - don't horde your scrolls and potions. A bag full of scrolls is useless if you don't put them to work. If you get a scroll of frenzy use it in the next three pulls rather than consuming valuable potions and reloading the game over and over. You will get another one. It's not like it's the last scroll in the game.
2) Retreat, avoid, and attack from different directions - if you find yourself getting overwhelmed by a pull first consider if there is a way around it. Could you sneak past the bandits? Could you just run from the dragon or lead him to a city where you can take him on with support? Is there a choke point that you could use to take enemies on one at a time?
3) Use the environment - Take note of traps, narrow corridors, and nasty falls. The computer is dumber than you...hopefully. Remember that nasty swinging door trap that one shotted you? It might be able to one shot them too. Can you get a bunch of enemies on a narrow bridge and push some of them off?
Edit: If you would like to contribute, in the spirit of the thread, please number your specific insights.