It look like you miss the overall mitigation. Your presented numbers show only the damage reduction by avoidance and partly by block.
The mitigation number also annoys me a little, when looking at the actual web stats. It seems it combines mitigation from block and from shields cast by Priests or Paladins. The block thing belongs to the tank while the shield spell mitigation is just another form of healing.
One interesting example would be comparing the Fog an Ashra stats. Both fights lasted 2 minutes and 51 seconds. Fog took 831,196 over the course of the fight while Ashra took 1,070,424 damage over the same amount of time. So the druid took quite less damage than the warrior.
From the Gais, Buffs & Debuffs tab i can see that Fog is using the
[Defender's Code] which is most likely the main reason the Druid took quit less damage.