With a hotfix that went out to all realms at 2:35 p.m. PST (about 10 minutes ago), we’ve greatly increased the amount of XP you’ll get alongside followers.
Throughout the PTR, your XP was reduced by 20% per follower, so if you ran a dungeon with two friends and two followers with you, XP was reduced by 40%. If you went in solo with four followers, XP was reduced by 80%.
Now in the live game, each follower causes a 5% XP reduction. Your party of three players and two followers should see a total of 10% reduced XP, and solo players with four followers receive a 20% reduction.