Yes, thats exactly the problem: For absorbs the logs don't show how big the values are per cast but by how much the reduce the hits taken.
This is also why there are no 'over-absorbs' on the logs ever even if quite a lot absorbs get wasted due to the target they are placed on not getting hit before they expire.
Calculating ineffective absorbs - while an interesting value in itself; even more so than overhealing - cannot be done by looking at the logs alone, currently.