I was wondering : will the legendary spells appear as frequent as normal ones or there is some kind of rule which stricts them, if they appear at all. ( I mean through various effects like discover or random spell generation.)
Because there are already legendary spells , the Quests. they do not appear, but its for a reason, they need to build your whole deck around them, but, and thats my point, also some of the legendary spells need you to. / Zerek's Cloning Gallery is pretty bad if your deck not contains special minions with effects, Flark's Boom-Zooka also needs some preparation. Kangor's Endless Army worthless, if you are not a mech deck and there is Myra's Unstable Element.
On the other hand, it would be hillarious if i could discover The Storm Bringer 3 times together with The Runespear in a midrange swarm-style shaman deck.