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The problem with allowing an offhand weapon in a fighting style for it is that it then has less room. I think instead the Adept of The Mysterious Circle feat should be a good pick for dual wielders, single one handed weapon users, and dueling fighting style uses.
This one may be more in the descriptor for controlling enemies tangents of attack
so its named it to invoke Thibaults
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I am currently making the Paragon Path : Adept of the Mysterious Circle. And hunting for good flavor text. I have a couple of powers started
I have a character whose Blade Song is interpreted as less magical than a sort of meditative focus which allows him to create a visual overlay in his mind, essentially projecting an Augmented Reality display in his field of vision (like iron man). He sees the circle of his own fighting space, those of other creature he can see, and all the tangent lines that connect and intersect within those, as well as the concentric circles of range, sound, normal focus, etc.
So, when he is missed due to his Int bonus to AC, he is seeing that line of attack and the opportunity, and where and how he can move his body and weapon to avoid or intercept the attack.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.