They can't catch you if you're on fire!

[Dauntasa]

When someone's literally covered in flames it should apply to disarms as well, since you're trying to wrestle something out of their hands(which are on fire).

I've always imagined disarm as more along the lines of slapping it out of their hands in the girliest way possible. Plus gameplay wise that'd be super OP

Not really. You could still disarm them, but you'd also be on fire then. You'd still be able to pull the usual strategy of running up to the man with the lightsaber and snatching it right out of his hands and decapitating him with it, but if he was also engulfed in flames now you are also engulfed in flames.