Heh, before this conversation gets out of hand, I would like to point out that I was able to (not be lazy) and test out the bug on the PTR. It has been fixed for both Hemo and Tendon Rip.
You can see it most notably here:
[19:29:55.556] Reesilol Shred Raider's Training Dummy 13753
[19:29:58.804] Reesilol casts Shred on Raider's Training Dummy
[19:29:58.804] Reesilol Shred Raider's Training Dummy *27288*
[19:30:00.605] Hyena casts Tendon Rip on Raider's Training Dummy
[19:30:00.805] Reesilol's Mangle fades from Raider's Training Dummy
[19:30:00.805] Raider's Training Dummy afflicted by Tendon Rip from Hyena
[19:30:02.116] Reesilol casts Shred on Raider's Training Dummy
[19:30:02.364] Reesilol Shred Raider's Training Dummy *25881*
[19:30:05.182] Reesilol casts Shred on Raider's Training Dummy
[19:30:05.182] Reesilol Shred Raider's Training Dummy 1 (O: 12923)
[19:30:08.743] Reesilol casts Shred on Raider's Training Dummy
[19:30:08.754] Reesilol Shred Raider's Training Dummy *1* (O: 26520)
[19:30:11.219] Reesilol casts Shred on Raider's Training Dummy
[19:30:11.627] Reesilol Shred Raider's Training Dummy 1 (O: 14125)
[19:30:12.324] Reesilol casts Shred on Raider's Training Dummy
[19:30:12.446] Reesilol Shred Raider's Training Dummy *1* (O: 28671)
[19:30:15.721] Hyena's Tendon Rip fades from Raider's Training Dummy
[19:30:15.827] Reesilol casts Shred on Raider's Training Dummy
[19:30:16.079] Reesilol Shred Raider's Training Dummy *20779*
World of Logs - Real Time Raid Analysis
You'll have to excuse the overkill part. Some hunter had the Ghostcrawler pet and for whatever reason was doing the TO THE GROUND ability, causing the dummies to have 1 HP.