Some numerical analysis of the high end, for your perusal. This isn't so useful for "normal" people, but for specialists who have 10+ skill in things. Still, it gives you a ballpark for how many successes you can expect the best people to give. Not very many, but I'm guessing we're really going to be rolling for 9s...

Note that if we are rolling for 11s, it's all about skill; even 5 dice with 10 skill will rate 2.4 successes. Of course, getting people with 10 skill is tricky.

Tom

Dice Skill Target Rate
9 10 11 3.3
9 15 11 4.3
9 20 11 5.0
9 10 9 5.1
9 15 9 6.1
9 20 9 6.8
12 10 11 3.8
12 15 11 4.9
12 20 11 5.8
12 10 9 6.2
12 15 9 7.3
12 20 9 8.2
15 10 11 4.3
15 15 11 5.5
15 20 11 6.5
15 10 9 7.3
15 15 9 8.5
15 20 9 9.5
18 10 11 4.7
18 15 11 6.0
18 20 11 7.1
18 10 9 8.3
18 15 9 9.6
18 20 9 10.7
21 10 11 5.0
21 15 11 6.4
21 20 11 7.6
21 10 9 9.2
21 15 9 10.6
21 20 9 11.9
24 10 11 5.3
24 15 11 6.8
24 20 11 8.1
24 10 9 10.1
24 15 9 11.6
24 20 9 12.9