Northrend RDF experience bug

Hello there,
i'm leveling character on Lordaeron and i do a lot of dungeons but i've noticed something real strange.
If someone can help or explain me why finishing dungeons do not grant experience. (you only receive 33000 exp +2 [Emblem of Triumph] for 1st dungeon of the day) i can confirm that works and for rest of dungeon you do not get any experience for finishing dungeon.
I've noticed it few times, killing last boss in dungeon pop up bubble that dungeon is complete even in chat you are announced that you received ~16500 exp, that is written with yellow letters, normal the exp is written with blue letters. So when last boss is down i get notified of everything and i only receive exp for that boss kill ~900 exp and nothing else. It seems real strange that this is bug and i cant find reports of it anywhere. Asked few time in chat ppl say: what is difference its only exp equal to one quest, but still its a bug. IF someone know something about this i would like to know.