In my latest fort, I got an Earthkin immigrant, then a Vampire mage, then an airkin, all in one immigrant wave. I was pretty excited by this, a chance to try the magic stuff (which I haven't seen much of yet!)
However.. well, something seems wrong with them. For one thing, the Earthkin and vampmage both move EXTREMELY slowly, as if they are always carrying a rock. No idea why, they don't show any wounds or scars.. but it's impossible to get them into action in any useful time. Not only that, but I sent them to kill a little troglodyte camp sitting in my cavern - just 3 poorly armed trogs. Much to my surprise, the trogs won handily, despite their garbage equipment - the Earthkin's stoneskin didn't seem to help much, and while the description of the Vamp mage says he can instakill an enemy to satiate his thirst, he seemed to only want to "sap the strength" of the trogs. You would think that rock skin + sapped strength would be a power-combo, but it seems not; neither one lasted more than 10 seconds.
After that, I decided to savescum a bit to test, sending them on random suicide missions (plenty of those on this map.) I've sure never seen the vamp do any insta-kill thing. He did turn a changeling breeder into a gargoyle once, though.. that promptly got destroyed by a Dark Strangler wrestler >.> This came up in-game us "changling breeder turns to Nothing", and it was referred to in the logs as Nothing, didn't show up in the animal list, and couldn't be assigned. Also to note, neither the vamp or the earthkin could even take a Strangler. Sadface, but the slow-moving thing makes them pretty useless anyways, I guess.
Not very impressed with magic so far, to say the least. At least the Airkin does ok. Pretty funny watching him wrestle things to death after webbing them.