Rae is not necessary if you can dominate the early board, whereas Fault may be questionable to not include. Then again, there are always more ways to make poop tiles or dervishes.
Kha is just strong as at least a 1-turn boardwipe with proper setup. Especially if the enemy doesn’t expect Kha in a bird deck, might be the reason why it’s working for you. Also OTK Vaath so we have that.