This doesn't happen. The first dungeon drops gear of the same iLv and defense, and the same stat limits as the previous expansion's max iLv minus 10 -- the same as base final tomestone gear. The second dungeon drops gear of the same iLv and defense and the same stat limits as the previous expansion's max iLv -- the same as augmented final tomestone gear or final savage tier gear.
The third dungeon finally drops higher iLv gear, and when you compare full augmented tomestone gear to a set of third dungeon gear, the augmented tomestone set is consistently behind the third dungeon set by a whole chest piece. That is, running around in a full set of the previous cap's augmented gear is the same as wearing a full set of the third dungeon's gear with either the chest or legs slot empty.