Blizzard's explanation on proc rate is that it is a factor that is used on AOE spells so that overall crit chance achieves a single spell. Use this as a reference, a proc rate of 0.5 is way too high for storm chaser, it is very easy to cast two twisters at the same time and have them hitting something. Same argument goes for 0.25 (energy twister's proc rate in 1.03). But Blizzard nerfed the proc rate to 0.125 for all the runes. This means we need EIGHT twisters at the same time to achieve the proc rate of a single hitting spell. Now with 8 twisters, that is 35 * 8 = 280 Arcane power, which is your entire arcane refill twice if you do not cast any spell. More like 4 - 6 times if you need to cast diamond skin, frost nova, energy armor, teleport, and explosive blast
Each twister lasts for 6 seconds. I dont know about other players, but I found it very difficult to refill my arcane power fast enough to cast 8 twisters to achieve the desired proc rate of a single hitting spell for two reasons. The first one is the cool down is not fast enough, i.e. I am not procing CM fast enough. The second reason is that I do not have enough arcane power to do so. Note that I have 50cc unbuffed, and 70cc buffed (with pinpoint energy armor, and deep freeze on frost nova). I personally found it very difficult to have eight twisters going at the same time, let alone many players with less cc. I agree with one of the posts above APOC seems to be working as AP with a chance to OC.
Now what is a good proc rate, i think 1/6, roughtly 0.18 is a good balance. That requires us to cast 6 twisters at the same time to achieve the same proc rate, which seems reasonable to me.
With wizard, we do not have many variety. with melee wizard, it is in many cases about which rune to use, rather than which skill to use. I have no problem with nerf the proc rate on ww and sc, but i do believe they are over nerfed to a point the build are completely killed (if player with 50+ cc wont use it, I dont know how many player will).
Thank you for reading this and pass them on, Lylirra