At first I hated the rotgland gun but it ended up being one of my favourite weapons, partly because it has no maximum range which made it especially good for bosses, cant remember the boss names but the "flying" boss where you end up on floating platforms was so easy once I had a powerful rot gun, I just stayed miles away from the boss on a platform far out of the bosses reach and let the rot do all the damage
I didn't know about its range, that definitely makes it better.
Picked up the last missing cipher a couple of days ago. Still need to try out the DLC.