I posted this back on the old forums, but with the Handsome Collection coming out, the farming spot is going to be available to everyone soon, plus some people will be completely new to Borderlands 2 and wonder where the best spots for tubbies are.
A lot of people like to run the Dust at night, or use the 4 player glitch and go to caustic caverns, but those runs often are more time consuming than productive. That being said, there is an area where you can go that seems to have a high chance of tubbies without 4 players or anything special. Vault Hunters, step into the Natural Selection Annex and welcome to the Creature Slaughterdome. There is one very simple rule to follow and you’re set.
- Accept round one of the slaughter, fight through till the final wave, but NEVER complete it, either save and quit or die at the end by the final few spiderlings or other lesser spiderants. Saving and quitting is faster on PC than dying, but on console the difference in time is about the same. If you are absurdly overpowered and feel that you may kill the last few, save and quit once you realize there is no tubby or after killing it. Krieg, for example, either really needs to watch what he’s doing or spec out of Bloodsplosion since he is capable of bloodsploding pretty much all of that 4th wave by accident.
There seems to be a high chance for a tubby spiderant to spawn after killing the matriarch and a few elemental spiderants in wave 4, and after killing him you can simply die and run it again. If he’s not there, die and run it again, NEVER COMPLETE THE MISSION. The other rounds do not have this high tubby chance. ALWAYS STAY ON ROUND ONE. If you accidentally complete it, dashboard quickly without saving. You also have a chance at a tubby skag in either wave one or three, and I’ve seen the tubby spiderants in waves 2 and 3 as well. It’s fast, it’s easy, and seems to be much more efficient in the long run. I have tried the dust and caustic caverns, but round one has just been so much more productive as tubbies just show up like mad in there. Sometimes you get a dry spell, but we all get those with any type of farming really.
EDIT: Neumeusis had a good point, the 4 player glitch does increase your chances, but also will make it very challenging for solo play, especially at OP8.
TL;DR: Do creature slaughter round 1, kill tubby in wave 4, die before finishing the round or save/quit, rinse and repeat.