Taking my own advice, I've done the Winter Veil quests five times now, once for each of my 60+ toons. I think I've narrowed down the probabilities on the various reward items for those of you with limited time. Milk and Cookies seems to only reward a collection of food items, most of which are low level. Metzen the Reindeer appears to only reward Preserved Holly, and the chance to preserve another small stack on the follow-up. The quest that reliably gives a recipe is the Abominable Greench one, which sadly is also the most difficult due to over-camping.
Luckily I've taken advantage of my mis-matched server hours to run the quests around 2-3am server time (11-12 for me). I've also done it a couple of times first thing in the morning (around noon, server time) which is another a good window to try. In both cases I've either been the only one there or seen 1-2 other groups loitering about.
Something I've noticed that other people don't do is ride around and look for him to spawn. They seem to kind of clump in a location and wait. Since the Greench has at least 4 spawning locations that I'm aware of, it makes sense to increase your coverage my riding between to 2 or 3 of them until he pops. I've had no trouble getting him this way, as other groups just sit in one spot and completely miss him when he spawns in another. So if you want to make sure you get him, mount up and loop through the area. If there's competition for him, you'll be able to get there faster in addition to covering more ground. You can also ride right through him if you need to tag him quickly, heheh.
From the Greench quest, I've gotten a recipe every time. Unfortunately for me, so far it has been recipes I didn't need. I got the Tailoring pattern once, the Alchemy recipe three times and the Engineering recipe once. All I really need is the Leatherworking one, I was hoping to get that this year, but so far no luck. I'll have to wait until the presents under the tree are activated and see what I get then.
I'm also disappointed that they didn't beef up the quest selections with some Outland-level recipes or add Jewelcrafting to the mix. I mean, having Winter Veil outfits and apple cider is nice, but since they were already on the job they surely could have reviewed the reward recipes too. It just seems odd to me that they have so many level 70 players now and didn't update the holiday content in recognition of that fact. I think the only nod to level cap players is the apple cider, which is pretty minimalistic in my view. Oh well, maybe next year Santy?