46.
Took off all gear other than legendary daggers. with 1.7% expertise, and 1.44% hit
fighting the raid training dummy (lvel skull, so assumed 3 levels higher than self. On the first killing spree, 1 of the offhand attacks missed.
View image: Wo WScrn Shot 100712 170125
will continue testing for further results.
EDIT: After some more Killing sprees (17 in total) I came up with some interesting data.
I have a total of 119 killing spree hits and 99 killing spree off-hand hits, this is not the 7, 7 I expected. When i first saw discrepancy in the number of hits, I started watching the combat log and counting hits. It looks like the number off attacks can clip from the offhand as well as the main hand. I had one killing spree hit 8 times with mainhand and 6 with offhand and other times have it hit 7 main hand and 5 offhand. It appears that some offhand attacks may be lost for some reason.
To conclude the answer to 46, after 200 total killing spree hits with 1.7% expertise, there were 0 dodges or parries, but there were several misses (20 main hand or 16%, and 12 offhand or 12.1%)
View image: Wo WScrn Shot 100712 170125
View image: Wo WScrn Shot 100712 170125
23.
Thus far it looks like it can be applied by white attacks and can proc the heal off white attacks and main gauche.
After subtracting misses, the number of melee attacks and main gauche is equal to the number of heals i "casted"
View image: Wo WScrn Shot 100712 182757
This was after a data reset once the poison was applied.
With that in mind ill do some testing on other abilities.
EDIT: after 100 sinister strike, 402 melee (59 miss) and 91 main gauche there (534 total hits) were 533 heals from leeching poison. one attack to apply the poison, 100% chance of a heal after that.
EDIT2: 100 Revealing Strike, 326 melee (-47) and 83 main gauche (462 total hits), 459 heals occurred which i think is safe to assume revealing is also 100% chance to proc a heal
Edit3: 80 shivs, 1236 melees (-166) 174 main gauche, 1324 total hits 1324 heals occurred. accidental reset all data in the middle of the test, so i lost the opening hits that apply the poison.
Shiv not only heals 5% of your health, but also procs the 10% of the damage heal