Update: a few minutes after publishing this, I found a pretty nasty mistake in the spreadsheet's workings. Basically, I was taking the difference between the base armor/resistance mitigation and the full mitigation in the wrong place, throwing the results way off. I've re-written my conclusions appropriately. This is why one shouldn't be theorycrafting at 6AM, even when suffering from extreme insomnia.
There's a serious problem with pet talent calculators. Something I'd half-expected Wowhead to get right, but apparently not.
The problem is that while they go to all that trouble to give you a pretty talent window with shiny icons, and making sure you don't spend more points than you have...
...none of them tell you what the talents do.
Oh sure, they'll tell you that Rank 10 of Great Stamina gives your pet an additional 40 stamina.
It's a bit like going into a quaint little bakery in a small town, and asking of the proprietor the contents of his pies. He then launches into an in-depth exposition on the low-level chemical composition of the pies, what particular local supplier he purchased the meat from, etc.
And then you say, "that's all well and good, but what do they taste like?"
The baker replies: "I have no idea."
This is not, on the whole, desperately helpful.
This looks like a job for theorycrafting! After a number of hours of fiddling randomly with a spreadsheet, as well as referring to Petopia , I came up with the Pet Calculator. This should work in pretty much everything except Microsoft Office; if you're using that, you might want to try the OpenDocument Format plugin. If there's demand, I'll try to rig up something for the Excel users, but without a copy of Excel, there's only so much I can do.
Before I go further, I just want to point out that the working in this spreadsheet could be, and the first time I published this was, wrong. That said, I've now double-checked it a few more times, gone over my reasoning again, and can't see anything obviously wrong with it. If you do find something wrong or just suspicious, please let me know.
Usage is pretty simple: on the first sheet, you plug in the various bits of information it demands of you like so:
These are the details for Tiddles and myself. You just need to edit the non-bold cells to match you and your pet's stats. Once you've told the spreadsheet all this, it will update the output section with the results.
The first two, "Pet Health" and "Pet Armor" should be pretty close to what's reported in-game. I've seen a few points difference here and there, but it's possible that it's just rounding differences.
"Effective Health" is talking about how much actual damage your pet can take, after taking armor and magical resistances into account, before going to the big stable in the sky.
"Absorption contribution" tells you how much of that effective health each of the Greater Stamina, Natural Armor and Resistance pet talents are responsible for. For stamina, this is just done by applying all the various modifiers to the stamina granted by Great Stamina and then converting it into health.
Armor and magical resistance is a little trickier: these are computed by working out the effective health (including base armor, armor and resistance from the hunter, etc.) followed by the effective health assuming we didn't have any points in Natural Armor of one of the resistance talents. We subtract the latter from the former, and this gives us the extra absorption spending those points give us. It's important to do it like this because the benefit provided by armor and resistances aren't linear; computing them by themselves would give an inflated result.
Finally, "Absorption per point" just takes the absorption contribution and divides through by the number of training points you spent on that talent. In this case, we can see that magical resistances are incredibly point-efficient compared to stamina and armor, by a full order of magnitude in the case of the former.
This lets you play around with theoretical set-ups; for example, investing 150 TP into Greater Stamina will give you just over half the absorption that those same points in Natural Armor would have given you. But of course, that's only in the case of physical damage.
Magical Resistance is also interesting. Rank 5 of any magical resistance will give you almost four times the absorption of stamina, at just under half the point cost.
That said, the resistance talents seem to give the biggest bang for the buck. Taking a Sporebat as an example, max ranks of Stamina and Armor only provide 5% and 8% of the final absorption respectively. That said, with rank 11 of Great Stamina, max rank Magical Resistance provides a whopping 30% of the final absorption.
Now, generalisations are always bad, and you should take your own circumstances into account, but it seems that in general:
Natural Armor is better mitigation for the points than Great Stamina is, assuming you're only interested in physical damage. That said, since the amount of absorption armor gives is relative to the amount of health you have, Great Stamina actually increases the effectiveness of Natural Armor. Might be interesting to set up a graph of the two...
That said, choosing to put points in one or the other exclusively, Stamina and Armor end up being about the same effective health for physical damage, but with Stamina also boosting your effective health against magical damage.
Irrespective of that, Magical Resistance blows them both out of the water and into orbit.
So there you go. Plug your pet and yourself in and see what happens. If you're looking to max out your pet's health, and just want numbers to plug into the pet training window without having to read all of that pesky text; assuming a baseline pet (like a Sporebat) with max-rank Bite or Claw, Rank 2 Avoidance and Rank 1 Cobra Reflexes plus 15 TP spent on a family-specific talent (leaving 266 TP to play with):
Rank 11 Great Stamina and Rank 5 Natural Armor seems to give the best physical absorption.
Rank 9 Great Stamina and Rank 5 Magical Resistance seems to give the best magical absorption.
If you want a bit of both, you'll just have to decide for yourself.
Again, if you spot anything wrong with this post or the spreadsheet, let me know.
Some have claimed that Wowhead's introduction of pet comparison tables, pet talent calculators, etc. have made Petopia obsolete. This is complete rubbish; where, pray tell is Wowhead's detailed tables of base pet statistics, or their pages on the formulae underpinning hunter pet health and armor?
Don't get me wrong: the new Wowhead stuff is very cool. They've got the best pet talent calculator I've seen, and the tables are much easier to use than static ones on Petopia. But Petopia is still t3h awesome.