They do pop on TVHM. I got the achievement last night and it didn't feel as if I had to farm too long for them.
You don't even have to have the quest active in Pete's bar, actually if you don't there will probably be more enemies to farm. But if you do have the quest active you also get 20 Torgue tokens each time, plus those you pick up in the bar. By doing this, I have plenty of tokens to buy a legendary now, just have to decide which one... Any thoughts on that?