Except Hunters killing spirits is also a game mechanic and even non Hunters are able to combat beast and spirits without use of the Old Blood or insight. Rom holding the Red Moon back isn't really a combat oriented feat, but more like a special ability that's just tied to Roms death. If were mixing lore with game mechanics then all of the Great Ones and Kin of The Elder Blood are weak to normal every day things like fire and electricity and earthly weapons. In all honesty the Great Ones in Bloodborne don't really show that great of power. What you're saying now is mere speculation of what they're actually capable of doing.
@codevein: Except Witcher lore states that only another Higher Vampire has the means to kill another higher vampire. Geralt can also kill ghost, but it still doesn't mean he and the hunter actually have a shot at killing a higher vampire like the Unseen Elder. And the Great Ones aren't even that powerful for real seeing as how they have simple weaknesses like how the Moon Presence is susceptible to fire and others are weak to poison or electricity.
@codevein: The Bloody Crow isn't really that impressive speed wise seeing as he's using The Old Hunters bone which just allows him to teleport short distances in small burst. Nothing new that the Quad team can't handle easily. And if that's the case Talion, Kratos and to an extent Geralt can just slow there surroundings down (Talion with Wraith, Kratos with Talisman of the Realms, Geralt with Witcher Mutations) and easily catch and kill him by then. Aloy can just deploy traps and do long range damage.