I decided to take a new character on the trip because most of the folks who were upset about losing Magnus were playing new toons. They had no way to purchase his recipes because the trinket from Eva Sarkhoff was no longer obtainable. In fact, Eva has been completely removed. So the classic quest to get her trinket and use it to see Magnus the friendly ghost has been gone for a while now. Unfortunately this didn't stop folks from wanting his recipes, specifically the Transmute Water to Air recipe. It seems that Essence of Air is fairly difficult to collect in bulk, so Alchemists were hoping to use the transmute for it.
I happen to have a mage that I've been leveling who is also my junior Alchemist. Since she's been a bank toon for the last 5+ years, she's done very little classic content. I took her out to Western Plaguelands to see what it would take for her to purchase from Magnus. As it turns out, not much. I found him inside the Smithy at Caer Darrow as soon as I arrived. I didn't need the trinket or any quests to see him. He's a ghost NPC, so he's not very visible unless you know to look for him. He is friendly to Alliance and Horde characters, and there does not appear to be any prerequisite quests to interact with him.
For those of you who missed out on the transmute recipe, be sure to visit Magnus the next time you're in the northern part of Eastern Kingdoms. He also has a rare pattern that might be of interest for our Blacksmithing completionists out there.
Please let me know if you run into any other undocumented tradeskill changes and I'll feature them in a blog post as well!