I've noticed on my priest (not sure if this applies to other classes) that my ratings are a bit off when I compare the tooltip to my stat sheet and remove/swap the item.

Here's my legs for example:

And my stat sheet (using deja character stats):

And then here's my stat sheet with the legs removed:

The crit from the legs said it was worth 1.91%, but removing them dropped me 1.94%.
Similarly, the mastery was listed as worth 4.31%, but removing them dropped me 4.40%

I also see the same thing with stats like leech:


Then trinket removed:

It went from 14% to 11.79%, but if the trinket was worth 2.76% it should have dropped to 11.24%.

This applies to all stats, including swapping gear (though the numbers get a bit harder to follow so I went with removing gear).

Maybe this is an artifact of the diminishing returns? Though I believe I was well below the cap on the crit at least.

Let me know if any other information would be helpful!

I'll be honest, it probably does have something to do with how DR is calculated. I haven't looked at how DR is calculated since it was originally introduced and I'm not 100% positive if my way of calculating it is perfectly accurate. I wrote the code for calculating DR with no way to test it as I don't really have any way to force my stats to the different DR thresholds.

should be fixed (in theory) in latest release

So i think I actually figured this one out. I was playing around with some gear and noticed a difference on stuff that shouldn't have been affected by DRs. I took a look at the stat scaling data and apparently at some point from my initial release with the data for levels 60+ and now, blizzard decided to completely change all the stat conversion rates for all levels.

Since I use a hard coded table for that data (since I can't find a way to dynamically pull it from the game) when they changed all those numbers, my data didn't update and as such resulted in incorrect calculations.

I did a quick local test and it seems to have fixed it (at least from what I can tell) so I will just have to update all those conversion rates and then it should work correctly .......

In theory.