Wow, where to start. lvl 58 right now. Act 2: Hell, and still going through enemies pretty nicely. Had a stump for a while, just had to level up, save money and upgrade.
Ok. It sounds like you are just a bitter gamer man. Wizardry should be done at a range. So load yourself up with skills that allow you to do things from a distance, and use the shields if they pull you in.
Some skills you said you didnt like, or were no good...
Disintegrate, quite useful, especially with chaos nexus, allows you to be run, stop, shoot beams that will always strike a target, and then keep running.
Mirror Imagine with Simulacrum...your images get more life, and I dont know about you, but when used properly, they always chase the images before they chase me, while i stand in behind and unload on them.
Diamond Skin: Crystallize...also useful, lasts long enough and has a low enough recharge time that you an basically use it repeatedly along with energy armor, so long as you leave enough distance for the recharge time to expire before you get hit too much.
Energy Armor: Energy Tap .... gives you a boost of skill power.
Arcane Orb: Obliteration....i have this as my primary weapon, it hits hard and you can fire it from a distance if your aim is solid. Also takes out grouped enemies!
Your 4th skill should be something powerful, personally I go with the archon, its my desperation skill. I think energy twister does the next most damage.
Back all that up ith Evocation, Astral Presence, Galvanizing Ward....or if you like Glass Cannon or Temporal Flux.
If you are getting pwned by certain creatures, either you strategy sucks, your level isnt there yet, your equipment is not up to par, or a compbination of these. Work Harder, Complain Less.