I recently attempted to get the moon-moon pet on my hunter, there was a group of around 25 alliance and another group of around 15 horde. Thing was the horde pulled and like the timeless isle bosses, moon moon isn't faction tagged, so anyone who participates, be it alliance or horde is eligible for loot.
As it was one of the other people in my raid group got the pet which i didn't mind as she too is a pet collector. I got the moon-moon mount (which only lasts a week bah) and a DM fair quest item. But if you take into consideration the pet is awarded randomly to one player, and that the mob is not a faction tag mob then you'll have to figure out if you want to go through the process of making a raid, killing the mob (Moon-moon hits hard and has a major one shot ability when she pounces) as well as large damage dealing AOE effects, or buy it on the AH.
Given the spawn rate for moon moon, and the fact I've seen three of the pets up on the ah for between 9-11k gold I may well save up and buy it.
For those of you who want to fight it however here are some things to remember.
1/ She has a very high health pool
2/ She can be tanked, however the tank needs to have their own healer that can keep up with the damage
3/ She is tagable by any level that can enter the darkmoon fair
4/ At various points in the fight she will cast a starfall like ability, this is easily avoidable as you will see the circle on the ground before your hit, allowing time to move.
5/ When Moon-moon does her pounce ability, she will turn away from her current target and face another attacking mob. you have about 2-3 seconds before she pounces in which to move away. (This can cause the most wipes as it is is an instant kill AOE so anyone near the targeted person will also be killed - if moon moon is targeting someone who is NOT in the raid, you might not have the chance to move)
6/ apart from that this is a dps her down race she will go down eventually to combined might, but if you should die, then the GY is not actually that far from her spawn point also there are no adds in this fight, only the initial wolves that will spawn to begin with.
Good luck all, and i hope this helps.