There are at least 2 ways to get rid of many DRs rather quickly.
1. Get an advanced flamethrower (or a flame turret or something else splash-attacking) to help you in Dried Marsh area. Kill them spawning insectoids to get to the building. Kill three insectoid queens and grasp the egg and hoverbike blueprints. Build and upgrade the hoverbike. Someone already said how to play off with DRs and snipers. Just lure them to kill each other ; ) *EDIT* Oh yeah, don't forget to read how to upgrade the hoverbike in the journal. You normally won't see that message when you make hoverbike. *END EDIT*
2. Raise the alien pet (with brown -> reaper -> dire reaper corpses) to its final level. With its aid and inside Hoverbike Mark II (maybe also holding some turret to aid you), you'll be able to withstand MUCH, really MUCH.
3. (just IMO, I wasn't able to try that) If you're able to get to the portal (Ship Graveyard -> Communications Array) before you accomplish everything needed for 1 and 2, you can find Battledroid Blueprints in there (at least that's where I got them, AFAIR). You can make these guys to aid you instead of aliens (or with them, but not very comfortable with hoverbike, Battledroids move pretty slowly). Since you can't craft Replicator Cells with those Factory Programs, you're limited to that many Battledroids, how many Replicator Cells have spawned in your game. Still many of 'em.
To not cuddle the game down with DR corpses, feed them to your alien pet, eat them or create Hyper Recovery Packs (Ether + Reaper corpse + DR corpse).