I am by no means an expert on killing this guy, but I've done it twice and it seems there was ample time to complete the kill, even with some people running around crazy.
Today, after the patch, I tried Redfang and apparently ran out of time when he got to 8 PCT health.
This happened a second time, but I figured I just simply ran out of time. However, I had more DPS present than either of the times I had succeeded previously, and no one was running around. I left the zone, but returned later.
First run we ran out of time, Redfang around 8 pct.
Next run we ran a timer, and he depopped after 10 minutes, again at about 8 pct.
We ran it again, doing better with our DPS, and reached 8 pct at 9 minutes, and he depopped.
Finally, to verify our thoughts, we ran it again, and at 9 min 30 seconds he depopped, again at 8 pct.
Speaking with other experts on the matter, they suggested this must be bugged. Please advise.