You're right (Destiny)

by Ragashingo , Official DBO Cryptarch, Tuesday, October 06, 2015, 17:26 (3432 days ago) @ someotherguy

Guardians and their Ghosts can be killed outright by standard heavy bombardment. That's how Petra got demoted and that's what the Cabal have observed or theorized. Ascendant Hive can be blasted all they want outside of their throne worlds and be just fine.

My thought is the Hive's immortality is based on their worms and The Darkness and ours is more tied to the Travelers subtle changes to the universe and that the two are far more different than they appear. The Hive conquer and destroy, but even at its most dangerous and most desperate the Traveler gently influences the world around itself.