Warhammer Online has instituted a new system with patch v1.01. The "overkill xp penalty" is intended to balance the amount of experience gained by AOE groups as opposed to "normal" individuals/groups. Check out the official word on the subject:

Good evening!

As many of you may have noticed we introduced an "Overkill" XP penalty system in version 1.0.1 that was targeted at reducing the amount of bonus experience certain careers (or combination of careers) gained in very rapid, mass AoE killing situations. The change was specifically targeted at bringing the amount of XP gained more in line with the XP that an average player ( or group ) could achieve. We firmly believe that AoE capable groups should get a bonus to their experience and level faster. However, that bonus should not eclipse any other form of experience gain by such a large margin as it had in the past.

Unfortunately, since releasing this system to the public servers we have discovered a small number of instances where the lower limit on the system was affecting solo players too dramatically. As such we are temporarily disabling the penalty until we can properly evaluate and fix these occurrences. We are committed to offering a fair and balanced playing field to everyone.

See you on the Battlefield!
- The Warhammer Online: Age of Reckoning Team

Sounds fair but those of you playing will have the final word. What do you think?