understanding jack of all trades

[gryfn]

jack of all trades , trades a -1 Multiplier Penalty for a -1 Dice Penalty with all skills
assuming 2d6 gives a average roll of 8 with the doubling rule
given a stat of 1 your average roll with out jack would be 0
given a stat of 1 your average roll with jack would be 7
given a stat of 2 your average roll with out jack would be 8
given a stat of 2 your average roll with jack would be 14
given a stat of 3 your average roll with out jack would be 16
given a stat of 3 your average roll with jack would be 21
given a stat of 4 your average roll with out jack would be 24
given a stat of 4 your average roll with jack would be 28
given a stat of 5 your average roll with out jack would be 32
given a stat of 5 your average roll with jack would be 35
so the difference between the average shrinks by 1 each level
7, 6 ,5 4,3 ...
so if im right a cosmic 8 mind would roll the same ether way
and a cosmic 9 mind would be hindered by jack of all trades
am i understand it ?

[Dustland]

If all you're considering is the mean/average roll, then yes. I think if you look at the range or the possible scores, you'll see there is still an advantage to taking JoAT IF you're willing to risk a lower average in return for a higher potential outcome.

[Lindharin]

I haven't broken it all the way down, but on a quick look the math makes sense. But I'm okay with just acknowledging that anyone with Agility 5 + Cosmic Grace 20 and Mind 5 + Cosmic Thought 20 (so 50 pts just on those two stats) is far beyond needing a Jack of All Trades and is a master of every skill...

[gryfn]

I'm OK with it too , i just wanted to be sure i understood it.
thanks