That assuems the Naaru actually bother to persuade people through logic. X'era clearly didn't have such intentions when she tried to 'convert' Illidan, and as others have pointed out Turalyon actually loses the glow in his eyes after X'era is destroyed. If this means that he was freed of her sway over him, it wouldn't be unreasonable to have another Naaru Prime (or something even higher up in the Naaru hierarchy) take control again. It's probably easier for light-based beings to control light-wielding individuals rather than fel-wielding ones like Illidan anyway.
I don't really see Calia being enough of a threat even if she is controlled by the Light. She's merely a member of the Desolate Council and even if she suceeds in swaying half the Forsaken it's a minority in the Horde (which generally sways towards shamanism and druidism). Turalyon on the other hand is actin in stead of the High King and the Light is also very prevalent with the major Alliance races. Turalyon being controlled by the Naaru along with human/dwarven/draenei priests would be capable of far more damage than the Light having one seat in the Forsaken council.