The gauntlet has been thrown, the challenge has been issued. The showdown is on! And the winner is.... Black Morass <take a bow>.
I poked around Thottbot and tried to find some level 69-70 mobs for comparison to BM beasts. This was actually not easy as most of the beast-mobs in Netherstorm and Shadowmoon are 67-68. Perhaps this is part of the reason that leather drops suck, not enough 69-70 beasts to kill. The only place where it looks like you can find a decent number of level 70 beasts is in the Skethyl Mountains, so that is where I went. The saber kitties are kind of mixed in with the bird folk, and I really didn't want to fight bird folk and mess up my time-sink comparison. Luckily there are a couple of spots with just kitties, one by the cave to the west, which was sadly already camped. The other was at the southern edge of the lake right by the zone line and this is where I staked my claim.
There are about eight to ten spawns here and by the time I was done with the last couple of mobs, respawns were popping, around 10 minutes I'd estimate. These kitties have about 9k hitpoints, so they were very comparable to the BM mobs in terms of difficulty. They were also beating me down to about 30% each time and forcing me to heal after every fight, so not really the best grinding mob. But in the interest of comparison I stuck with them. In reality I think I'd probably go for 66-67 mobs so I wouldn't need to heal so much.
Here's the hard numbers:
Level 70 cats killed: 11
Level 71 cats killed: 13
Knothide leather: 16
Knothide scraps: 8
The blackwind sabercats have the best knothide drop rate I've seen so far, most of the 67-69 beasts I checked on Allakhazam had a 50/50 drop rate of scraps to leather. These cats were giving me about 2/3rds leather and 1/3rd scraps out of 24 kills. I was also able to kill almost twice as many of these compared to my 30 minutes in BM. Although I did die once in BM, which may have skewed my numbers.... oh well.
Anyway - if you don't want to waste time traveling to the Black Morass, this would be a reasonable secondary option. Not quite as efficient overall, but you do save in travel time. Personally I think I might hit BM for extended grinding and plan to spend a few hours there. Plus if you travel when you're not actively playing anyway, it wouldn't really count as part of the timesink.
I still plan to do a comparison of leather drops on the test server, but the dumb thing kept going offline every 20 minutes so I decided to work on this instead. I will still try to get those numbers to you this weekend if I can. Stay tuned!