This is really confusing: I checked it again just now (PTR client 14995, Brill EU realm) and it's now 15784/13983/12387... (both dungeon journal and item link, screenshot at http://i.imgur.com/KWLu3.png).
The odd thing is that the client is marked "Nov 11 2011", which is earlier than the date of your post (although perhaps they pushed it out late, not sure): I guess tooltips are now hotfixable, or perhaps they have a variable part that gets updated with stat changes from the server?
OK, I found out the reason of that: the amount scales with spell power (and I was wearing quite a bit of broken gear while checking...) and in addition is affected by the 4% increase from Master Shapeshifter.
After linear regression and rounding, the formulas of the Windward Heart healing proc tooltip (without Master Shapeshifter) seem to be:
Heroic version: (11726 + 13627) / 2 + sp * 1.411
Normal version: (10388 + 12073) / 2 + sp * 1.250
LFR version: (9203 + 10696) / 2 + sp * 1.107
The base value matches the average of the values listed on Wowhead and is not an integer, which probably means it's random in the listed range.
Sorry for the earlier confusion; note that the tooltip for Eye of Blazing Power instead does not depend on SP (not checked the actual effect).
From my observations on the PTR with Windward Heart (normal) has been:
DOES proc off of hot crits.
The spell proc is called "Nick of Time" (no PTR datamine link at the moment)
The ICD feels to be BELOW 45 seconds with some approximation by others (link). My testing in a 25 LFR raid suggests that a 25 second - 35 second ICD correlates to the proc rate compared to the fight duration (WoL Link) [Sephinia is the druid with the trinket]
Note: The windward heart trinket is seeing 6% - 9% of healing done over the course of a boss encounter.
Looking at the log (thanks for posting it!), the shortest inter-activation interval is 19.674 seconds, and the median of the intervals is (around) 25.245 seconds, so it seems the ICD must be 20 seconds.
Combining the healing per SP and ICD adjustments, it becomes the best trinket by far in Rawr, even as the model estimates only a contribution of 4.4%, while the log gives more as you point out (probably due to low damage and overhealing on other spells).