All the solutions I can think off is ugly.

-Ban those paladins (hard to justify that they exploited and it doesn't solve unfair gain problem Result:Lots of QQ, frustrated customers )

-Do nothing.(Means not fixing Unfair gain of achievements and loots situation. This includes not only pallies but any other player who was in the group with a pally . Also includes gained guild achievements. Result:Lots of QQ, frustrated customers)

-Roll back (means we delete last 2 days, go back in time to Tuesday morning. We start fresh. Every single player loose last 2 days effort. Result:Lots of QQ, frustrated customers, but seems fair)

I hope there is another solution which is better than these 3. I am sure Blizzard will do the best for community. but it is not easy decision this time.