Meh, with how this site works and with how people tend to make their characters here, its almost impossible for something to be OP based on racial attributes.
Just because something doesn't exist in the Force doesn't mean it can't be affected by it. I mean if I can use the Force to throw a Star Destroyer.... at something, I'm pretty sure he can't wave a voodoo wand and go "I don't exist in the Force so I ignore basic laws of physics and the Star Destroyer doesn't hit me". Also, didn't we rule Force Lightning is electricity, and not the Force?
The Jedi and Dark Jedi did use external-affecting Force powers against the YV. Only mental attacks and anything that tried to alter a state of their body was nullified.
Well, if you think about it, the Vong that survived went back to Zonama Sekot and went into the Unknown Regions to re-establish their relationship with the seed of their homeworld. I think, if the Vong were to return in small numbers, some of the could have regained their species' connection to the Force. Perhaps not enough to be concious of it but enough be apart of it once more.
Okay, after reading this, I've got to make a Yuuzhan Vong character... and yes, he will be a part of the Force. And he will be an atheist. And he will still be badass.