Just to clarify.. If you're tanking mobs in Stratholme, with a lvl55ish priest idling nearby, you can easily Shadowmeld, causing all mobs to jump on the priest. You can also shadowmeld if you get too many adds, to prevent death. Not sure you leave combat if you're with someone else, haven't tried, so dunno about armorswapping.
Shadowmeld is why I'm still on the fence whether to get a nelf or a human. But, it's basically Vanish (sorta) vs. 3expertise with swords, 10% more rep, AND
Every Man for Himself (free trinket slot in pvp yay). I also have no humans, and lots of nelfs, so I'm leaning towards human tbh.