These guys are worse than the Dothraki on Game of Thrones. Vex are machines that can self-replicate & pull copies of themselves through time. The Hive & Eliksni are both capable of giving birth to large numbers of offspring. But the Cabal ? I understand that the majority of the Cabal forces are clones, no problems there, but shouldn't we maybe, I dunno, find & blow up their cloning facilities ?