I have great trouble deciding what to do about the post. I want to tell you to first test, then post instead of saying you will do the testing later. But if I give you a point for that you will be banned and unable to post what you promised. So I'm only doing a warning now but I am expecting you to post something of the results of this test.
An absence of crit do not means that you are at 100% if you don't cast a big amount of spell, like a thousand. It's because of RNG. It's easier to see with recount/Skada if your at 70% instead of 80% than 95% versus 100%.
If you want a good way for testing it on a Dummy:
Lower your crit to ~20% (60% with Shatter)
Make a test without Debuff to have ~200 Ice Lance with FoF.
Make the same test with the debuf on the Dummy.
So if you have the ~60% and ~65% rate on Recount/Skada, it's not multiplied by Shatter. If you have ~60% and ~75%, it's multiplied.
I'm at work so I can't test it now. but I will right after.