I'm sorry but you do realise that precursors (their original form before the flood) literally can't die? Death has no concept to them they used to travel around in various forms many if which where none physical or even celestial. As for clone production try pumping out 1 sentinel that can destroy covenant carriers every 6 seconds. Also the FR can produce a Halo in less then 3 weeks while a Death Star takes how many months? Also the flood infect A.I turning them on their masters so not only do you have precursors flood forerunners ancient humanity (who were on par with the forerunners technology wise) the sanshy'um (prophets) the elites brutes grunts drones jackals and hunters but you also now have the thousand's? Millions? Of droids including the super droids droidika's and others but also a virus that can wipe out a planet with a single spore. SWU=screwed.