I agree that there's too many damage types. The biggest problem is that they're all the same! A fire ball does the same damage as a water ball. Aside from poison, all it is is a different resistance. It doesn't matter if you improve Fire Resistance of Water Resistance, because it will still resist the same percentage of attacks.
Diablo 2 made each element decidely different:
Fire - Well rounded.
Lightning - Fast but erattic.
Poison - Very powerful, but over time.
Freeze - Weak, but paralysing.
If you're going to select a resistance, you now have something to go on. Which one bothers you the most? If you want to select an attack, again, you now have options.
