So, while this incursion’s been up, I’ve been studying this world quest and think I’ve figured it mostly out.
Essentially, when a Vol’dun Incursion is up, the World Quest “Battle Bots” will spawn. During this World Quest, there will be a giant robotic Spider and Gorilla that will spawn that a gnome and goblin are repairing. They regenerate health at a set rate, however, the world quest allows players to help them regenerate energy. (You can also collect salt from the Krolusks you killed for the World Quest after completing the WQ to turn in to give energy as well) Every turn in grants the robot 5% energy.
In general, more energy increases the chance that your faction’s robot will win. However, it’s not a guarantee. There’s still a modicum of RNG in which abilities your robot decides to use. If it decides to be dumb and use only it’s regular attack, rather than a strong shield for instance, it’s going to lose. I’ve had the spider lose with 50% energy to the gorilla at 20%. Though I’ve never seen the Gorilla lose with more energy.
There’s also a bug at the moment in which the robots have a habit of de-syncing and despawning, thus they never battle. This will likely be fixed soon. Until then, if this is occurring on your server, use the group finder to realm hop, or wait until they sync back up, it usually happens within a half hour, and even then, it’s 100% normal for them to desync every other battle, as the one that loses respawns faster than the one that wins, but then they respawn together after the failed attempt at fighting.
Anyway. When your faction’s robot wins, a small barrel will spawn underneath the corpse of the other faction’s robot for about 30 seconds. You can loot this for a once per incursion piece of the battle pet. For example:
This means that only Alliance players can build the Rebuilt Mechanical Gorilla and only Horde players can build the Rebuilt Mechanical Spider. However, they are flagged at cageable.
The parts are flagged as unique, so it SHOULD only take 3 incursions to rebuild one of the battle pets, but I guess that depends on if the unique flag means we can’t get duplicates or if it means we simply won’t be able to LOOT duplicates.
Buuloki on wowhead summed up the basics in a comment on the respective pet pages, for those who prefer the wowhead method.