Back in the early days of my Summoner Wars career, I posted a thread where I listed all of the odds for making standard 1, 2, 3, 4, and 5 AV attacks:
Forum user kaszkiet made an awesome reference card that you can print out at home with all of these percentages:
If you'd like to print this, here it is in high resolution. I've rescaled the front and back to be the same size as Summoner Wars cards (58mm x 88mm) if you print it at 300 DPI.
Update: Forum user Lets play a game has provided this chart with even more details:
If you'd like to use a handy calculator for Units like Mook-backed Cave Goblins or Blagog, the following site found by Joepinion is also quite useful:
Probability of success - Enter (as a decimal) the probability of getting a Hit on 1 die. For example, hitting on a 3+ (normal AV) would give you .666667. Hitting on a 6+ would give you .1666667. Hitting a Mook-backed die (2+) would give you .833333333.
Number of trials - Enter how many dice you’re rolling
Number of successes (x) - Enter how many Hits you need
Binomial probability: P(X = x) - The probability of getting exactly how many hits you need
Cumulative probability: P(X < x) - The total probability of getting fewer Hits than you need (can be quite useful)
Cumulative probability: P(X < x) - The total probability of getting fewer or as many Hits as you need (not very useful)
Cumulative probability: P(X > x) - The total probability of getting more Hits than you need (not very useful)
Cumulative probability: P(X > x) - The total probability of getting as many or more Hits than you need (the most useful number, typically)