I don’t think that’s quite the case. The Bronze Dragonflight are like the Night Elves. The Night Elves are protectors of nature, but for the Kal’dorei, Nature tends to mean “forest”.
Simmilarly the Bronze flight seems to be working twoards preserving what they’ve designated as the Ideal Timeline. And they can be quite ruthless about it. What’s limiting them is that while they have the big picture, they don’t have all of the details, especially with the major power loss they suffered with the fall of Deathwing.
When we approached Anachronos he responded with ,“Is it time for you to visit me already? Yes, I suppose it is then.” This means that the Horde was meant to recruit the AU Mag’har per destiny.
Though it’s unknown if that meant that Garrosh going to AU Draenor was always meant to happen or if WoD reshaped a few details of the Main Timeline.
This right here, I’ve have the ever growing feeling that every Void Lord does not want the same thing. Perhaps if every old god was not made by the same Void Lord they also do not hold the exact same goals. As you said their are several times the old gods or old god aligned forces seemingly want the Legion to succeed, clearly that must be a flawed idea, Sageras would easily smash a old god like N’Zoth. So why would they want the legion to succeed? Are their corrupted legion agents on the void side? Is there a Void Lord who perhaps doesn’t want the others to succeed in breaking into reality? Why?