Don't know where this should be posted but so I thought here might be a good place.
I haven't seen anyone do any probability number crunching for heroclix so I decided to take a shot at it.
Columns are as follows (sorry about the extra 0's and stuff, I had to add lines and 0's to make everything line up.)
A - Number needed to hit
PH - Probability of hitting
SS- Prob of hitting if target has super senses (or another ability that reduces the chance of success by 1/3, such as Shape Change or Impervious)
2 SS - Prob of hitting if target has two powers that reduce the chance of hitting by 1/3 (such as SC and SS, or SC and IMP)
FP - Prob of hitting if you have prob control (Friendly Prob)
EP - Prob of hitting if your opponent has prob control (Enemy Prob)
BP - Prob of hitting if both you and your opponent have prob control (Both Prob)
I used Super Senses in this example, but the same probabilities hold for any of the 2 out of 6 rolls. SS, IMP, SC, Hypertime Team ability. With all of these you have a 33% chance of not being able to do what you want to do on top of the normal hit probability. You can also see why stacking two of these abilities on top of each other makes a figure even harder to hit. Even having to hit a 3 will only result in success less than half the time. That's why you put Entangle on Plasmus. If you are attacking with a 9, it's like you were attacking a 19 defense rather than a 17.
Also, for figures like AA The Question, is it better to perplex down defense by 1 or outwit SS? If the unmodified difference between attack and defense is 8 or less, outwit SS. If the unmodified difference is 10 or greater, perplex down defense. If the unmodified difference is 9, it doesn't matter.
Notes on Prob Control
With prob control you can hit a 9 almost as easily as a 7, and it makes hitting 7's or lower almost a sure thing. If your opponent has prob control it makes successful attacks much harder, especially above a 7. You go from a 58% chance to hit a 7 to only having a 34% chance. And it's not even worth trying to hit an 8 or higher with such a low probability of success. If both you and your opponent have prob control, things get a little weird. You actually have a better chance of hitting numbers 7 or below, but a worse chance of hitting 8 or above.
How should you use this in games? If you are the only one with prob control, make the most important attacks first. Use your prob control as soon as you need it. If your opponent has prob control (regardless of if you have it too) attack the easy to hit targets first, attempting to bait your opponent into making you re-roll an easy success. Then after they use their prob, attack the harder to hit targets (using your own prob control if you have it).
It's been a while since I've had to use my stats. I hope these charts are helpful. It was fun cooking them up.