Blizzard
Thanks everyone for the feedback.
We agree that our initial change made Invasions too unrewarding for characters who weren’t at max level, so we’ve just applied a hotfix that increases XP gains from killing Legion invaders. Since Invasions are only around for a short period of time, we want them to feel lucrative, and provide incentives to actively participate in them.
You should be seeing a lot more progress on your XP bar for helping your fellow Azerothians fight the Legion now.