Note that the 45% was just give by one person and confirmed by none.

The kind of data we need to sort this out is as follows:
  1. Character level and exact EXP before dungeon
  2. Character level and exact EXP after dungeon
  3. The exact lump sum bonus awarded as stated in the chat log
  4. Whether character was rested or not (and if the rested bonus got exhausted during the run)
Once we have these 4 data points from multiple people of same level and of different level, for the same dungeon, we can determine exactly how the bonus EXP is calculated.