Since I have confirmed (at least to my own satisfaction) that the pet GCD really is 1.25 seconds, then it stand to reason that for Rake to have the best non-loss uptime, it needs to fall off, but for the shortest possible time. There is no 'perfect' cooldown as there would be with a 1.5 GCD (9 seconds being both the CD and the bleed length). For the bleed to not lose any ticks there needs to be 8 other casts done (assuming endless focus) between Rakes. 9/1.25 = 7.2, but since taking that 0.2 cast off would lose us a tick it needs to be 8 casts... Well well well, that just happens to be *drumroll* 10 seconds. The original cooldown. Interestingly that fits my personal observations, I have noticed that the Rake bleed tends to fall off for a little while (I have Rake macroed to priority over Claw in the Steady Shot so that Rake will fire as soon as possible with no Claw locking it out), which would be around a second in my 1/3 Longevity spec... A 2/3 Long spec should see 7 Claws per Rake, and never see the Bleed drop.

While such delicacies are rare in this game, it is not impossible that Rake indeed designed around 10 second rotations being best.
Well that got me thinking, would it be possible to create a pet castsequence? Something like:

/castsequence reset=10 Rake, Claw, Claw, Claw, Claw, Claw, Claw, Claw, Claw

Obviously it is a bit bulky, but any sort of macro could lead to better Cat DPS with anything but a 1/3 Long spec. I guess I will have to try it out tomorrow, a bit late here now. But maybe someone has a better and more elegant solution to this.

Any definitive testing done as fas as Aspect of the Beast's "supposed" dps boost versus Aspect of the Hawk's dps in a raid setting? I have tried a couple times in raids and havent noticed anything insanely skewed, or even noticeably different but most of those fights have haven't exactly been a good environment to test in for one reason or another.

No. The Serpent Sting glyph increases the duration of Serpent Sting; that's all. It's the Steady Shot glyph that boosts Steady Shot damage when Serpent Sting is up.

EDIT: Eep, I'm over-thinking things. The Steady Shot glyph requires mats from Northrend, so Serpent Sting right now at 70 isn't really all that, although the glyph will be available at level 62 when the expansion arrives.

All you have to do to determine whether or not serpent sting is worth using at 70 is see how much damage it does per global cool down compared to just pumping out another steady.

With standard raid buffs, 7700 armor boss, though only sunders on target (my guild has lazy moonkins/locks)

My average steady shot hits for 1362 as BM with crits worked in.

With the same raid buffs a single serpent (glyphed) does 1931 damage
Even non glyphed it would be 1609

Now, I don't have 4pc T6 but 10% wont catch up that amount unless you also have an absurdly higher crit rate than me (hair under 32% unbuffed).
With 10% more armor on bosses soon the same boss will have 8470~ armor widening the gap farther.

So for me at least using a global cooldown every 18 seconds is an increase in damage done, at a slight mana consumption increase. Marks and SV hunters have chimera shot and lock and load giving them incentive, so all specs can make use of the sting even without steady shot glyph which will make this whole thing irrelevant.