-I swapped the 15/14 between Con & Dex to get Rain of Blows & to keep on track for the 19 Dex required for Flail Mastery at Epic, but beyond these two concerns I don't see any reason it couldn't be 15 Con/14 Dex
You need 15 Con for Plate Proficiency. So you'd either want to drop Dex to 14 or Wis to 13 if you were doing the build this way.
I understand the reasoning with the fighter build.
My problem is that people who dual wield as fighters make seriously 0 sense. It has utterly 0 benefit (at this point at least) and you could bump up a damage dice (not to mention other properties like high crit/brutal) by taking an honest to goodness 2 handed weapon.
Dual Strike is an incredible at will, particularly if you take advantage of Adventurer's Vault's overpowered damage-boosting items. Funneling Fury (level 1) and Hampering Flurry (level 7), both from MP, are fighter powers that take advantage of dual-wielding. Rain of Blows doesn't have advantage of dual-wielding, but if you meet the prerequisites (15 Dex + a flail does the trick) it's overpowered.
That said, dual-wielding fighters can be too strong, with damage comparable to a dual-wielding ranger (which does very high damage for a striker), plus the better hit points and class features of a fighter. The Ranger build gives you more skills, more multiclass, and a wider selection of powers that take advantage of your two weapons.