Storm Knight's DCs calculation

[d20familiar]

Hi, playground!

I was tinkering with Stormwind's Storm Knight (http://community.wizards.com/content/forum-topic/3429956) (basics spoilered below), and after several readings the explanation of those ECL1 DC17 gusts of wind still eludes me. Here's what I see:

1st level: 10 (base) + 2 (spell level) + 1 (Cha mod) + 1 (Mighty Dragonmark feat) = 14, instead of declared 17;
6th level: 10 (base) + 2 (spell level) + 1 (Cha mod) + 1 (Mighty Dragonmark feat) + 2 (Storm Sentry class level) = 16, instead of declared 19;

Gear (+2 CHA at ECL 6 is reasonable) still doesn't cover this 3-point gap, and at ECL1 one cannot afford even +2 stat-booster.

Half-Elf
Warblade 3 / Half-Elf Fighter 1 / Storm Sentry 2 / XYZ 14
Feats (considering 2 flaws):

1st Least Dragonmark (Mark of Storm - gust of wind)
1st Mighty Dragonmark
1st Dragonmark Prodigy (updraft)
3rd Dragonmark Mastery / Quicken Dragonmark
6th Lesser Dragonmark


Curious thing: iconic Storm Sentry, "Fighter 2 / Swashbuckler 3 / SS 4" with Least and Lesser Dragonmark feats, has the same 12 CHA and DC17 which actually matches the formula 10 + 2 + 1 + 4 = 17.

So, am I missing something crucial or is it a case of simple miscalculation?

[Karganak]

And now our entire group is tinkering with this build, trying to find ways to bump this DC to 17. =)
Result of DC 14 seems correct, yet in the original thread some quite observant people didn't have an issue with DC 17. Surely, someone here knows why?