i call bs on this, if an elf can get 1 MS on the faery in hostile with without 5+ fails beforehand then he certainly wont after hes gained acres and/or been massed. You have faery that is obliged to run mystic so is not going to be low wpa; not going to be massed in range in hostile, so not much damage can be done. On top of this, you get to cast MS all age and reel in the honour titles?
Thievery i agree with to some extent, since you pigeon-hole the faery into going mystic for ms, a halfer/rogue is going to have you for breakfast, with land coming in for a couple days