They’ve explained to BlizzCon that those changes target is the snowball effect. By removing experience from Forts and Keeps they want to limit the level gap that may already almost close the match after the first objective.
The team behind could always turtle up and defend while getting ready for the next team fight without being completly outmatched.
For sure is something that will help the casual players, but will also probably improve the overall fun of the game (just think of how many topics only on this board were talking about snowballing).
I don’t know if it’ll work, so we have to wait and see it when they’ll release it.