Most of the time, we ran into fan dubs that actually ruin the mood of a certain anime series, including vocaloid too. so recently, my friend posted this youtube cover who really pays the deal.
Her alias name is Sapphire. Mostly her covers run around a TV size of the anime songs, (less than or equal to two minutes) also her personal blog says she's a mad woman in the internet. Make sense though, when it comes to singing of up beats, or not, she's really good.
Here's some of her covers that may turn your belief about fan dubs. :)
1. No Game No Life - This Game
2. Sword Art Online - Ignite
3. Kill la Kill - Before my Body is Dry
4. Guilty Crown - My Dearest