It is not possible to read out stats from other units then yourself.
There is however the option to calculate your theoretical damage with a chosen ability (like it is done
here) and compare it with the actual damage.
By doing this, one could also create a database of the mobs resistances.
This is not possible with every Ability, since some can vary based on parameters that cannot be tracked. For some abilities it should be doable.
Unfortunately its a bit of work to do it in an addon because of all the cases that need to be covered.