Scroll of Transgormation added as a reward in Wintergrasp
I play in Lordaeron and Wintergrasp matches are only filled with less than 30 ppl per faction outside of peak hours. I've spoken to many players and to them there's little motivation to join especially when you have already done two VOAs.
This little incentive isn't game-breaking at all because Scroll of Transformation is a cosmetic item. In fact this will encourage PvErs to join.
I myself play alot of RBGs with the sole motivation on getting scroll.