I think the (relatively) easy access to the Blood of Dragons is a good thing. There is nothing more annoying when leveling up than to have to take only the spells you want at end game because you will have capped long before you could have switched everything. So the blood is a nice convenience, so long as it doesn't change the flavor of the game.
I would add a timer to the blood, because at present a sorcerer could essentially prep spells in anticipation of a specific quest at will, rather than this being a slow and difficult process. I think giving the blood a 6 or 9 day timer would ensure its utility while keeping the current flavor of sorcs and fvs.