The main issue we're having, is that we're running into bugs in Blizz's own code.
Our current road block as of right now, is that the available quests from an NPC (if there's more than 1) is not being populated. They've changed how its handled completely, and we're having a bit of a hard time finding the packet handler for the available quests dialog.
Proof: Try any of these Lua functions with a questgiver that has more than 1 quest available: GetGossipAvailableQuests(), GetAvailableQuestInfo(1), GetNumGossipAvailableQuests(). You'll notice that none of them work anymore. Blizzard is no longer populating an array that is required for these functions to actually return anything. (Inside their "GetQuestInfoFromIndex" type function, the first array is *always* empty which causes it to fail)
We're looking for the way they deal with it now, but its taking a bit longer than we'd like. (We're pulling our hair out trying to figure it out) There are actually very, very few things left that need to be updated/fixed. So bear with us.