I've spent the last few days combing posts here and the BNet forums reading a lot of updates and ideas. Hopefully you won't take the low post count as ignorance, as I've been trying to do my research. Anyway, after reading lots of ideas, I started running with something that takes a slightly new spin on Instability that I think is pretty slick, and I wanted to share it.
The Wizard's Instability gauge starts out empty, and as you cast spells it fills. Basic projectiles might only fill it 5% while more powerful spells will fill it faster. If you stop casting for a moment, the gauge subsides rather quickly. As a visual, you can imagine that in the middle of a heated battle it could be jumping up and down like a lie detector needle.
Casting a spell while the gauge is partial filled would give you a damage bonus, for example casting at empty is a normal 100% damage spell and when the gauge is filled your damage would buffed 125%. Talent or skills would allow you to increase your max instability damage buff to say 150% or something.
Simple spells would increase the gauge by a small amount, like magic missile will add a steady 5% instability to the gauge, but a powerful spell like blizzard would add 10-35% instability, providing some volatility to how quickly the gauge fills. If you decide to cast it with the gauge at 85% full, you may or may not max out the gauge and suffer the penalty.
I've read several good suggestions for the penalty for becoming too unstable, anything from self damage to a debuff to a stun. Personally I like the idea of feedback damage. You risk casting a spell at a high Instability level and it'll be stronger but you may suffer damage.
So the main strategy would be to have the player balance their spells and casting speed to stay on that razor's edge of high Instability without killing themselves.
Of course if you need to lay down some serious damage you could accept the feedback damage and spam your best spell and use your potion, or keep your eye on that health globe on the ground, etc...
Anyway, this idea seems to fit everyone's description of "Risk vs Reward" "Volatile" "Blasty" and still remains pretty simple. I hope you enjoyed my ramblings.
I think it's a creative idea, but since other classes so far will be able to spam their skills, it isn't enough to keep it fair for the Wizard. I'm all for diversity of skills, but spamming is honestly what Diablo is in many, many ways, whether we care to admit it or not. I think any energy solution should go beyond limiting the player.
I do think that was a good way to look at the problem from a different angle, though. Like from the top to the bottom.
This is a nice suggestion, but imo a random damage is not good penalty because it ends up being to luck dependent. Also, i don't think it should cost LIFE.
If i would desing the system i would do something like a overheat problem. It's like, if you acumulate to much instability, the bar will take exponentially more time to go back. And if you reach beyond 100% you are silenced for a period and takes alot of of time to cast a spell again. In other words my penalties would be:
-Progressively slower recovery of the instability bar.
-If you reach max, you're silenced.