According to Wizards & Wenches, Warhammer players have figured out how contribution in public quests and keep sieges is measured:
Now we know how contribution is calculated. It’s so shockingly simple, so obvious we wonder why we didn’t figure it out a long time ago. It isn’t.
See, instead of actually measuring all the data players do during Public Quests to find out who contributes the most every player is making a roll when they enter a zone, and that roll is your contribution that appear. It doesn’t weight all your healing, all your damage, all your buffing, or everything that make you more worthy of a reward than a player standing AFK in a corner. It’s just random. The roll remains until you zone so you will get the same contribution in both Keeps unless you relog or someone with higher roll enters the PQ area.
Wow. Honestly, I'm speechless. What do you say to something like that? The evidence presented in threads on the discussion forums looks solid to me.
This is a blunder on par with Age of Conan's "females do less dps than males because their animations are slower" bug.