Actually, they are identical. The difference you are seeing is that TorParse's damage taken calculations include absorbed damage. If you add the Abs and total column from PARSEC you get 303614 which is the same as TorParse's numbers. This difference in calculation affects all of the damage taken numbers.
Now which is right? I dunno. As a tank myself I can see the value in both calculations. I will think about it some more. And if you have any feelings about it, share them and convince me to change it