For only one dedicated night of collecting, I'd say I was very successful. I managed to collect all but a few wild pets from Draenor. The conditions on beta are ideal for collecting, though, so I don't expect my experience on live servers to be as lucky/quick. With more competition it will probably take more time to just find the new pets.
Unfortunately in a few cases, even without a ton of collectors searching for the same thing I was, some of the wild pets gave me trouble.
What a Pain in my...
If my experience on the beta is any indication of what it will be like on live, there are three wild pets (maybe more) that might give collectors a headache in WoD.
Both zones have appropriate places where they could spawn. Why implement them as exclusive secondaries when there's all this real estate for them to wander around?
The entire southern half of Gorgrond is a jungle that's filled with other birds, some of which are even wild pets too (Junglebeak). And there's a cluster of actual (bone) wind serpent mobs in Spires of Arak (they share the same model as the pet). It's a wonder to me that neither seemed to appear near any of these likely locations.
Perhaps they haven't been fully implemented yet? Did I somehow miss them? Was someone else clearing them out faster than I could spot them? Or maybe they're just really, really rare?
I have a problem with the last explanation, though. Even with the rarer wild pets of Draenor, there is usually some indication of where they could spawn. All you have to do is find the non-battle pet version of them to get an idea of where to hunt. The exceptions, of course, being the Axebeak Hatchling and Bone Serpent. They were nowhere to be found in any form when I looked. Maybe they're the new Minfernal/Unborn Val'kyr? I cringe at the thought...
Oh, speaking of non-battle pet versions of wild pets...
In the end I did manage to find a Shadow Sporebat, but only after many hours of fruitless looking and waiting. This particular pet gave me trouble for a couple of reasons.
Firstly, it's spawn location. The sporebat seems to appear alongside its larger counterpart, the Zangarra Sporebat. These mobs can only be found in the tiny little area in north-eastern Talador, Zangarra. And when I say tiny, I mean tiny (compared to other zones/areas). With such little space, there's probably only a limited number of spawns for that area.
Secondly, there ARE non-battle pet versions of the Shadow Sporebat hovering around the area. That's the only reason I knew to check there. But do they share spawns with the actual pets? I really don't know.
I decided to take it upon myself to try and coax the spawning of actual pet versions by killing off the critters. One would hope that by doing this, it would free up "slots" for the real pets to spawn in, right? Unfortunately, that didn't seem to help.
Another method that some collectors swear by is killing off the mobs associated with the pet. I didn't need to since Zangarra was full of people questing and therefore killing the Zangarra Sporebats for me.
Absolutely no battle pets were spawning. Not even miscellaneous wild pets, such as snails, rats, etc. It was only after I had left the area and checked back hours later that I found one lone Shadow Sporebat and managed to collect it.
I'm not a designer or developer so I don't know the finer details of how spawning works, but to me the tiny area in which the sporebat could spawn coupled with possibly sharing a spawn rate/timer with non-pet versions both made it very difficult to collect this particular pet. Not to mention that since there's a lot of traffic in that spot, questing and what not in such an enclosed area, it's possible that any pets that DID manage to spawn were instantly casualties of player versus mob battle.
Needless to say it was very frustrating, and this situation might end up applying to a few other wild pets as well.
From what I've observed, many of the wild pets that only spawn near/around their larger counterparts (the hippos for example) tend to have a similar problem as the Shadow Sporebat. It's not quite as bad for most of them since there are more areas in which they can appear (it's still limited for the hippos though since they only appear around bodies of inland water), but there were A LOT of non-pet versions wandering around. As adorable as they are, I was fairly annoyed whenever I came across one that I couldn't actually interact/battle with.
It would be nice if there was some official confirmation on whether or not killing the mobs and the non-pet versions actually helps the spawn rate. In some situations I did away with both, while in others I let both be and just hoped to come back and find a pet to battle. I really can't say which method worked better; both were equally aggravating because neither seemed to have any impact at all.
Anyway, these are just the few exceptions to the norm. And it's possible that I just happened to be extremely (like a million times) unlucky. Perhaps others will have a better experience with the aforementioned pets, and easily find their spawn locations. (Please let me know if you do!)
My overall experience with collecting wild pets in Draenor was good. The majority of pets spawned in logical areas, so it wasn't that hard to find them. I expect that due to higher competition on live servers there will be fewer spawns up, and the quality of spawned pets not as ideal (most were rare on beta). But that can be overcome with some patience and dedication. That's collecting in a nutshell for ya, I guess? ;P