I just went through TVHM, doing any side missions that gave 10k+ experience, and didn't give a blue or higher reward. It shouldn't be too difficult to hit 50 by the time you get to the Warrior.
Bar brawl, Tier 3. Repeatable for 9.7k each time, in addition to the kills. You can also hoard Tokens at the same time, and cash them in for level 50 legendaries.
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