I can attest that Jarvis' services are the most thorough, professionally laid out services i've ever dealt with by far. Each guild has it's own customized list of rules that are given to the purchaser before the run has begun. This waiver of sorts specifically states the loot regulations and play regulations expected of both the purchaser and guild. As a raid leader that has carried dozens through SoO already, i can not emphasize enough - the randomness of the loot drops. Most 14/14 purchasers walk away with 15-20 pieces of gear depending on class and amount of off specs they are interested in. This is also greatly impacted by the quality of gear the purchasing character currently has. Being that the drop chance of any warforged items is incredibly low, it can never be a guarantee to provide those items that would likely be the only upgrade to any of the permanent members of the carrying guild and thus taking precedent.
There are a small amount of guilds offering sales with the guarantee of certain amounts of loot, these typically come at a greatly elevated pricing bracket. The services offered by Jarvis and his affiliates is a content sale with guarantee of a mount if you paid for it, which is literally the only guaranteed item to drop in the instance. As a carrier i know we personally will do everything in our power to to make sure the purchaser is walking away as content as they can be with their run. If we could, we would love to assure everyone every drop they would want - that's just good business. Unfortunately it is not the way World of Warcraft is set up.
Again, the services provided and the professional presentation that Jarvis has developed are second to none, we can guarantee you will get your kills, lots of gear if you have poor gear already, mounts if you are buying them and an experience that will impress - playing along side some of the best!