RG Live WotLK 3.3.5a

First up: Using the database to get correct info on spells is not a good idea. Although it tries to show DBC data, some of it is interpreted incorrectly. Also, any spell property that doesn't come from the DBC is (probably) not shown at all.

So my first question is: Did you actually observe these spells missing ingame?
You said it "returns a miss on both ‘Corruption’ and ‘Shadow Word: Pain’" which I'm interpreting as the following scenario:
You have SW:P on your target, you cast Mind Flay, Mind Flay hits but SW:P is not refreshed and keeps ticking down
Or did you mean something else? If the above, does that happen while you're hit capped or only while you're not?

The second question is: Are you basing the theory that the dot is reapplied instead of being refreshed solely on your Inner Focus?

As soon as I cast my first Mind Flay (after I have applied Shadow Word: Pain with Inner Focus active), the DoT is REAPPLIED instead of REFRESHED.

--> https://www.mmo-champion.com/threads/697544-inner-focus-SWP (e.g.)

So my first question is: Did you actually observe these spells missing ingame?
You said it "returns a miss on both ‘Corruption’ and ‘Shadow Word: Pain’" which I'm interpreting as the following scenario:
You have SW:P on your target, you cast Mind Flay, Mind Flay hits but SW:P is not refreshed and keeps ticking down
Or did you mean something else? If the above, does that happen while you're hit capped or only while you're not?

From what I've been able to observe, it happens only when you're not hit capped. I performed a few tests on a heroic training dummy one with just the 6% from talents, one with 15,45% hit from talents and gear and one with 17,4% hit from talents and gear.

I've added a few screenshots from the tests with just the 6% from talents and the 15,45% hit from gear and talents. In both cases I've had the talent's passive effect miss, more so in the 6% situation.

In the case of the 17,4% hit (capped) test, I did an 11 min test with about 300 mind flay casts and did it did not return a pain and suffering miss (nor a mind flay miss).

I also observed that if mind flay misses the target, the Pain and Suffering effect is still applied. This is probably logical, since I gain the mind flay aura myself, even though the spell misses the target. I've also added a screenshot showing this scenario.

The second question is: Are you basing the theory that the dot is reapplied instead of being refreshed solely on your Inner Focus?

As soon as I cast my first Mind Flay (after I have applied Shadow Word: Pain with Inner Focus active), the DoT is REAPPLIED instead of REFRESHED.

No, I'm basing this on the fact that the talent's effect can actually miss on RG, which it should not, since it is a passive effect. If this is somehow normal (which I'm sure it is not), this would also apply to a glyphed Pestilence (DK) from example. Glyph of Disease adds a passive effect to Pestilence which refreshes your main target's DoTS. If the same would be true here, Pestilence would hit the target, without refreshing the Diseases on the target. I've personally never had this happen on RG.

--> https://www.mmo-champion.com/threads/697544-inner-focus-SWP (e.g.)

Well, I guess I'm wrong here then, this however does not make my ticket invalid. I've always lived under the assumption that this was possible and never had anyone say otherwise, thanks.