Google Doc (8/23/12):
If anyone else is willing, some of the numbers need independent verification. The notes at the bottom of the image explain some of the anomalous results I found.
June 5th Update:
Frenzy - Sidearm confirmed to grant LoH by Miigzz.
June 9th Update:
Frenzy - Sidearm results still anomalous, couldn't verify Miigzz results.
Revenge - Grudge and Overpower - Revel confirmed to grant 33% LoH.
HotA - Rolling Thunder still doesn't seem to grant LoH.
Image changed to GoogleDocs spreadsheet.
June 13th Update:
Image added back per request.
Frenzy - Sidearm axe still not giving LoH: http://www.youtube.com/watch?v=_EScuohD6qo&t=0m45s
June 18th Update:
Wyatt Cheng confirms that LoH ratios are actually proc ratios used for all barb skills:
July 3rd Update:
As Nubtro pointed out on the 3rd page, some ratios have changed. I was able to verify that WotB - Slaughter's 'blood explosion' AoE damage no longer grants LoH and that Weapon Throw - Dread Bomb is now only 25% per target. Unspecified 1.03 patch change or experimental error, either way, thanks Nubtro!
August 23rd Update:
Five changes made as listed in the 1.0.4 patch notes, see second page of Google Doc for details.