I'm pretty sure the amount of badass rank has nothing to do with it. Its the number of challenges you complete that counts towards the tokens. That being said, lower levels have low requirements on their challenges, but with a high level trying new stuff around, you can unlock a massive amount of challenges really fast, faster than a new character. After a while tho, a new character will be needed, but my point was, dont disregard the potential token gains from playing a newly high level character, they work VERY well.

Hmm, I've read and heard that more BA rank, more ranks you need for next token each time. I don't know then, my bonus won't be that high anyway, because I probably won't even level my another char to 50.
Agreed that it helps "a lot" if you switch to weapon/s that you haven't used etc

yeah, and you get access to more possibilities later on, so its easier to farm tokens, until you are maxed ofc